Fix validation error type `PR04` and check in CI

[kynan]

Problem description

In order to have a continuous check by the CI on validation error PR04 (Parameter "{param_name}" has no type), tackling them from the current code base enables the addition to the CI for automated testing in the future.

PR04 has just 12 occurrences (see overview of the errors):

method	file	file_line	github_link
pandas.core.resample.Resampler.std	pandas/core/resample.py	797.0	https://github.com/pandas-dev/pandas/blob/master/pandas/core/resample.py#L797
pandas.Grouper	pandas/core/groupby/grouper.py	30.0	https://github.com/pandas-dev/pandas/blob/master/pandas/core/groupby/grouper.py#L30
pandas.core.groupby.GroupBy.rank	pandas/core/groupby/groupby.py	1811.0	https://github.com/pandas-dev/pandas/blob/master/pandas/core/groupby/groupby.py#L1811
pandas.core.groupby.DataFrameGroupBy.rank	pandas/core/groupby/groupby.py	1811.0	https://github.com/pandas-dev/pandas/blob/master/pandas/core/groupby/groupby.py#L1811
pandas.Panel.apply	pandas/core/panel.py	1000.0	https://github.com/pandas-dev/pandas/blob/master/pandas/core/panel.py#L1000
pandas.Panel.transpose	pandas/core/panel.py	1270.0	https://github.com/pandas-dev/pandas/blob/master/pandas/core/panel.py#L1270
pandas.Timedelta	None	NaN	https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.max	None	NaN	https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.min	None	NaN	https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.factorize	pandas/util/_decorators.py	559.0	https://github.com/pandas-dev/pandas/blob/master/pandas/util/_decorators.py#L559
pandas.read_parquet	pandas/io/parquet.py	255.0	https://github.com/pandas-dev/pandas/blob/master/pandas/io/parquet.py#L255
pandas.io.formats.style.Styler.render	pandas/io/formats/style.py	421.0	https://github.com/pandas-dev/pandas/blob/master/pandas/io/formats/style.py#L421

Todo:

• get rid of the errors in the code base
• update the code_check.sh script to take into account the PR04 type of errors

[mwoss]

Hi. May I work on this issue? :)

[mwoss]

I have no idea how to fix Timedelta docs. I cannot locate file with that class.

[thoo]

@mwoss Timedelta docs might be there: pandas/_libs/tslibs/timedeltas.pyx . You need to rebuild the extension. python setup.py build_ext --inplace -j 4

[mwoss]

@thoo Thanks you a lot :) I will look at that file.