Trying to save audio to mp3, saving to wav instead

Question

I am making a project for class and the chatbot I have waves the file to .wav instead of .mp3 like the project requires. I do not know how to save it to mp3.`

import streamlit as st
from bokeh.models.widgets import Button
from bokeh.models import CustomJS

from streamlit_bokeh_events import streamlit_bokeh_events

from gtts import gTTS
from io import BytesIO
import openai
import uuid
from pydub.playback import play
from pydub import AudioSegment

openai.api_key = 'my_key'

if 'prompts' not in st.session_state:
    st.session_state['prompts'] = [{"role": "system", "content": "You are a helpful assistant. Answer as concisely as possible with a little humor expression."}]

def generate_response(prompt):

    st.session_state['prompts'].append({"role": "user", "content":prompt})
    completion=openai.ChatCompletion.create(
        model="gpt-3.5-turbo",
        messages = st.session_state['prompts']
    )
    
    message=completion.choices[0].message.content
    return message

sound = BytesIO()

placeholder = st.container()

placeholder.title("Group 4 Voice ChatBot")
stt_button = Button(label='SPEAK', button_type='success', margin = (5, 5, 5, 5), width=200)


stt_button.js_on_event("button_click", CustomJS(code="""
    var value = "";
    var rand = 0;
    var recognition = new webkitSpeechRecognition();
    recognition.continuous = false;
    recognition.interimResults = true;
    recognition.lang = 'en';

    document.dispatchEvent(new CustomEvent("GET_ONREC", {detail: 'start'}));
    
    recognition.onspeechstart = function () {
        document.dispatchEvent(new CustomEvent("GET_ONREC", {detail: 'running'}));
    }
    recognition.onsoundend = function () {
        document.dispatchEvent(new CustomEvent("GET_ONREC", {detail: 'stop'}));
    }
    recognition.onresult = function (e) {
        var value2 = "";
        for (var i = e.resultIndex; i < e.results.length; ++i) {
            if (e.results[i].isFinal) {
                value += e.results[i][0].transcript;
                rand = Math.random();
                
            } else {
                value2 += e.results[i][0].transcript;
            }
        }
        document.dispatchEvent(new CustomEvent("GET_TEXT", {detail: {t:value, s:rand}}));
        document.dispatchEvent(new CustomEvent("GET_INTRM", {detail: value2}));

    }
    recognition.onerror = function(e) {
        document.dispatchEvent(new CustomEvent("GET_ONREC", {detail: 'stop'}));
    }
    recognition.start();
    """))

result = streamlit_bokeh_events(
    bokeh_plot = stt_button,
    events="GET_TEXT,GET_ONREC,GET_INTRM",
    key="listen",
    refresh_on_update=False,
    override_height=75,
    debounce_time=0)

tr = st.empty()

if 'input' not in st.session_state:
    st.session_state['input'] = dict(text='', session=0)

tr.text_area("**Your input**", value=st.session_state['input']['text'])

if result:
    if "GET_TEXT" in result:
        if result.get("GET_TEXT")["t"] != '' and result.get("GET_TEXT")["s"] != st.session_state['input']['session'] :
            st.session_state['input']['text'] = result.get("GET_TEXT")["t"]
            tr.text_area("**Your input**", value=st.session_state['input']['text'])
            st.session_state['input']['session'] = result.get("GET_TEXT")["s"]

    if "GET_INTRM" in result:
        if result.get("GET_INTRM") != '':
            tr.text_area("**Your input**", value=st.session_state['input']['text']+' '+result.get("GET_INTRM"))

    if "GET_ONREC" in result:
        if result.get("GET_ONREC") == 'start':
            placeholder.title("You can speak now!")
            st.session_state['input']['text'] = ''
        elif result.get("GET_ONREC") == 'running':
            placeholder.title("Transcribing")
        elif result.get("GET_ONREC") == 'stop':
            placeholder.title("Click Again To Ask Another Question")
            if st.session_state['input']['text'] != '':
                input = st.session_state['input']['text']
                output = generate_response(input)
                st.write("**ChatBot:**")
                st.write(output)
                st.session_state['input']['text'] = ''
#conda activate voice_recognition_software
                tts = gTTS(output, lang='en', tld='com')
                tts.write_to_fp(sound)
               #filename =  f"SpeechFile_{str(uuid.uuid4())}.mp3"
                st.audio(sound, format="audio/mp3")

                st.session_state['prompts'].append({"role": "user", "content":input})
                st.session_state['prompts'].append({"role": "assistant", "content":output})

`

I have tried both exporting from the bytes (aka "sound" in the code) and also changing the format of the st.audio (st.audio(sound, format="audio/mp3"), towards the end) it now just saves it to an empty file type (just .). Maybe the streamlit format is not correct, idk. The documentation is terrible on this subject