Getting error message when trying to get at risk numbers below KM-plot (lifelines)

Question

I've used lifelines a lot, but when I'm re-running old code that previously worked fine I get the following error: KeyError: "None of [Index(['At risk', 'Censored', 'Events'], dtype='object')] are in the [index]"

I'm guessing there has been some changes to the code when displaying at risk counts, but I can't find any evidence of it in the lifelines documentation. I am using version 27.0

Snippet of the table with data

index	t2p	O
1	354	False
2	113	False
3	1222	False
4	13	True
5	59	False
6	572	False

Code:

ax = plt.subplot(111)
m = KaplanMeierFitter()

ax = m.fit(h.t2p, h.O, label='PPI').plot_cumulative_density(ax=ax,ci_show=False)

add_at_risk_counts(m)

Full error:

KeyError                                  Traceback (most recent call last)
<ipython-input-96-a8ce3ea9e60c> in <module>
      4 ax = m.fit(h.t2p, h.O, label='PPI').plot_cumulative_density(ax=ax,ci_show=False)
      5 
----> 6 add_at_risk_counts(m)
      7 
      8 

~\AppData\Local\Continuum\anaconda3\lib\site-packages\lifelines\plotting.py in add_at_risk_counts(labels, rows_to_show, ypos, xticks, ax, at_risk_count_from_start_of_period, *fitters, **kwargs)
    510                 .rename({"at_risk": "At risk", "censored": "Censored", "observed": "Events"})
    511             )
--> 512             counts.extend([int(c) for c in event_table_slice.loc[rows_to_show]])
    513 
    514         if n_rows > 1:

~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\indexing.py in __getitem__(self, key)
   1766 
   1767             maybe_callable = com.apply_if_callable(key, self.obj)
-> 1768             return self._getitem_axis(maybe_callable, axis=axis)
   1769 
   1770     def _is_scalar_access(self, key: Tuple):

~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\indexing.py in _getitem_axis(self, key, axis)
   1952                     raise ValueError("Cannot index with multidimensional key")
   1953 
-> 1954                 return self._getitem_iterable(key, axis=axis)
   1955 
   1956             # nested tuple slicing

~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\indexing.py in _getitem_iterable(self, key, axis)
   1593         else:
   1594             # A collection of keys
-> 1595             keyarr, indexer = self._get_listlike_indexer(key, axis, raise_missing=False)
   1596             return self.obj._reindex_with_indexers(
   1597                 {axis: [keyarr, indexer]}, copy=True, allow_dups=True

~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\indexing.py in _get_listlike_indexer(self, key, axis, raise_missing)
   1551 
   1552         self._validate_read_indexer(
-> 1553             keyarr, indexer, o._get_axis_number(axis), raise_missing=raise_missing
   1554         )
   1555         return keyarr, indexer

~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\indexing.py in _validate_read_indexer(self, key, indexer, axis, raise_missing)
   1638             if missing == len(indexer):
   1639                 axis_name = self.obj._get_axis_name(axis)
-> 1640                 raise KeyError(f"None of [{key}] are in the [{axis_name}]")
   1641 
   1642             # We (temporarily) allow for some missing keys with .loc, except in

KeyError: "None of [Index(['At risk', 'Censored', 'Events'], dtype='object')] are in the [index]"