DOC:fix EX02 plot.line and parallel_coordinates

[zgdjcls]

          Hi I'm going to work on:

pandas.plotting.parallel_coordinates
and
pandas.DataFrame.plot.line

Originally posted by @zgdjcls in #51236 (comment)
But when I run the docstrings I got this error:
Partially validate docstrings (EX02)
<doctest pandas.Series.xs[5]>:1: PerformanceWarning: indexing past lexsort depth may impact performance.
df.xs(('mammal', 'dog'))
Traceback (most recent call last):
File "/Users/zhengyiming/Desktop/pandas/./ci/../scripts/validate_docstrings.py", line 494, in
main(
File "/Users/zhengyiming/Desktop/pandas/./ci/../scripts/validate_docstrings.py", line 429, in main
return print_validate_all_results(
File "/Users/zhengyiming/Desktop/pandas/./ci/../scripts/validate_docstrings.py", line 373, in print_validate_all_results
result = validate_all(prefix, ignore_deprecated, ignore_functions)
File "/Users/zhengyiming/Desktop/pandas/./ci/../scripts/validate_docstrings.py", line 329, in validate_all
for func_name, _, section, subsection in get_all_api_items():
File "/Users/zhengyiming/Desktop/pandas/./ci/../scripts/validate_docstrings.py", line 360, in get_all_api_items
yield from get_api_items(f)
File "/Users/zhengyiming/Desktop/pandas/./ci/../scripts/validate_docstrings.py", line 137, in get_api_items
func = getattr(func, part)
AttributeError: type object 'CombinedDatetimelikeProperties' has no attribute 'unit'
Partially validate docstrings (EX02) DONE

I'm not sure why it says 'CombinedDatetimelikeProperties' has no attribute 'unit', is this my environment issue? How should I fix this

[MarcoGorelli]

Hi - my guess is that you didn't follow everything in https://pandas.pydata.org/docs/dev/development/contributing_environment.html ?

[MarcoGorelli]

closing as per #51236 (comment)