Maximum recursion depth exceeded with nltk recursive descent parser

Question

Before I show the code I'm working with, I want to say that I can usually tell when I'm going to get an error. It's when I have a rule like the following:

DetP -> DetP PP
S -> S Conj S
VP -> VP PP

It's usually when an item is on both sides of the arrow. If I test a sentence after changing a rule to make it like that, I'll get infinite recursion. Based on my reading, though, that should be allowed. And I also have rules like

AdjP -> Adj NP | Adj AdjP

which didn't cause errors, so I'm confused.

Here is my code.

import nltk
import spacy
import re

nlp = spacy.load('en_core_web_lg')


def make_grammar_string(sentence):
    doc = nlp(sentence.lower())
    nouns = [f'"{token.text}"' for token in doc if token.pos_ == 'NOUN']
    verbs = [f'"{token.text}"' for token in doc if token.pos_ == 'VERB']
    adjs = [f'"{token.text}"' for token in doc if token.pos_ == 'ADJ']
    preps = [f'"{token.text}"' for token in doc if token.pos_ == 'ADP']
    dets = [f'"{token.text}"' for token in doc if token.pos_ == 'DET']
    advs = [f'"{token.text}"' for token in doc if token.pos_ == 'ADV']
    prons = [f'"{token.text}"' for token in doc if token.pos_ == 'PRON']
    auxes = [f'"{token.text}"' for token in doc if token.pos_ == 'AUX']
    advs = [f'"{token.text}"' for token in doc if token.pos_ == "ADV"]
    
    grammar_string = f"""
    S -> DetP VP | DetP VP CS
    CS -> Conj S
    NP -> Pron | N
    VP -> V DetP | V | V DetP PP | V PP | Aux DetP | Aux DetP PP | Aux PP
    AdjP -> Adj NP | Adj AdjP
    DetP -> Det NP | Det AdjP | Det AdvP
    PP -> P DetP
    AdvP -> Adv AdjP | Adv Adj
    V -> {' | '.join(verbs)}
    Det -> {' | '.join(dets)} | ε
    Adj -> {' | '.join(adjs)}
    N -> {' | '.join(nouns)}
    P -> {' | '.join(preps)}
    Pron -> {' | '.join(prons)}
    Aux -> {' | '.join(auxes)}
    Adv -> {' | '.join(advs)}
    Conj -> "and" | "but" | "or"
    """
    return grammar_string

def make_sentence_tree(grammar_string, sentence):
    doc =  nlp(re.sub(r'[.,?:;]', '', sentence.lower()))
    input = [token.text for token in doc]
    # print(grammar_string)
    # print(input)
    grammar1 = nltk.CFG.fromstring(grammar_string)
    print(grammar1.productions())
    trees = []
    rd_parser = nltk.RecursiveDescentParser(grammar1)
    for tree in rd_parser.parse(input):
        trees.append(tree)
    trees.sort(key=lambda x: len(list(x.subtrees())))
    t = trees[0]
    t.pretty_print()

s = "The boy kicked the ball down the street"
mst = lambda s: make_sentence_tree(make_grammar_string(s), s)
mst(s)

The traceback is

Traceback (most recent call last):
  File "/Users/gbcrockett/Desktop/python/conlang/nltk_practice.py", line 104, in <module>
    mst(s)
  File "/Users/crobotnik/Desktop/python/conlang/nltk_practice.py", line 103, in <lambda>
    mst = lambda s: make_sentence_tree(make_grammar_string(s), s)
  File "/Users/crobotnik/Desktop/python/conlang/nltk_practice.py", line 79, in make_sentence_tree
    for tree in rd_parser.parse(input):
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 130, in _parse
    yield from self._match(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 168, in _match
    yield from self._parse(rtext[1:], newtree, frontier[1:])
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 130, in _parse
    yield from self._match(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 168, in _match
    yield from self._parse(rtext[1:], newtree, frontier[1:])
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 130, in _parse
    yield from self._match(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 168, in _match
    yield from self._parse(rtext[1:], newtree, frontier[1:])
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 130, in _parse
    yield from self._match(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 168, in _match
    yield from self._parse(rtext[1:], newtree, frontier[1:])
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 225, in _expand
    yield from self._parse(
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/parse/recursivedescent.py", line 126, in _parse
    yield from self._expand(remaining_text, tree, frontier)

......

File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/tree/tree.py", line 544, in convert
    children = [cls.convert(child) for child in tree]
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/tree/tree.py", line 544, in <listcomp>
    children = [cls.convert(child) for child in tree]
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/tree/tree.py", line 544, in convert
    children = [cls.convert(child) for child in tree]
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/nltk/tree/tree.py", line 544, in <listcomp>
    children = [cls.convert(child) for child in tree]
RecursionError: maximum recursion depth exceeded

I asked ChatGPT, and it recommended making a rule like S' in the case of

S -> S Conj S

So S' -> Conj S, then S -> S S'. It also said that S -> S Conj S is fine the way it is, depending on when I asked it. ChatGPT seemed confused. I'm not sure if a rule like S -> S Conj S or DetP -> DetP PP is doable with nltk. I think it should be doable, but I'm not sure.