DOC: building page for nested methods doesn't work

[MarcoGorelli]

The following

python make.py --single pandas.Series.str.rsplit

fails to produce the docs:

(pandas-dev) marcogorelli@OVMG025 doc % python make.py clean && python make.py --single pandas.Series.str.rsplit
Running Sphinx v4.4.0
loading translations [en]... done
making output directory... done
[autosummary] generating autosummary for: index.rst
[autosummary] generating autosummary for: /Users/marcogorelli/pandas-dev/doc/source/reference/api/pandas.Series.str.rsplit.rst
building [mo]: targets for 0 po files that are out of date
building [html]: targets for 1 source files that are out of date
updating environment: [new config] 2 added, 0 changed, 0 removed
reading sources... [100%] reference/api/pandas.Series.str.rsplit                                                                        
WARNING: autodoc: failed to import method 'str.rsplit' from module 'Series'; the following exception was raised:
No module named 'Series'
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
/Users/marcogorelli/pandas-dev/doc/source/index.rst:44: WARNING: 'any' reference target not found: getting_started
/Users/marcogorelli/pandas-dev/doc/source/index.rst:60: WARNING: 'any' reference target not found: user_guide
/Users/marcogorelli/pandas-dev/doc/source/index.rst:77: WARNING: 'any' reference target not found: api
/Users/marcogorelli/pandas-dev/doc/source/index.rst:94: WARNING: 'any' reference target not found: development
writing output... [100%] reference/api/pandas.Series.str.rsplit                                                                         
waiting for workers...
generating indices... genindex py-modindex done
writing additional pages... search done
copying images... [100%] _static/index_contribute.svg                                                                                   
copying static files... done
copying extra files... done
dumping search index in English (code: en)... done
dumping object inventory... done
build succeeded, 5 warnings.

However, it works just fine to do

python make.py --single pandas.Series.value_counts

I haven't figured out how to address this, so opening an issue for now