Fix validation error type `PR04` and check in CI
#### 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](https://gist.github.com/198cfa552c727d71bd7360fda66fdbb4)):

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