API: Signature of UDF methods
There are many signatures of pandas methods that take a UDF. If I've missed methods, please let me know and will update.

Below, `other_arg` is a placeholder for 1 or more keyword arguments, and `value` is a placeholder for the default value.

Signature: `func, other_arg=value, args=value, **kwargs`

 - [Series.apply](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.Series.apply.html)
 - [DataFrame.apply](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.DataFrame.apply.html)
 - [Expanding.apply](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.window.expanding.Expanding.apply.html)
 - [Rolling.apply](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.window.rolling.Rolling.apply.html)

Signature: `func=None, other_arg=value, *args, **kwargs`

 - [Series.agg](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.Series.agg.html#pandas.Series.agg)
 - [DataFrame.agg](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.DataFrame.aggregate.html#pandas.DataFrame.aggregate)

Signature: `func, other_arg=value, *args, **kwargs`

 -  [Series.transform](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.Series.transform.html#pandas.Series.transform)
 - [DataFrame.transform](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.DataFrame.transform.html#pandas.DataFrame.transform)
 - [DataFrameGroupBy.filter](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.groupby.DataFrameGroupBy.filter.html)

Signature: `func, *args, other_arg=Value, **kwargs`

 - [DataFrameGroupBy.transform](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.core.groupby.DataFrameGroupBy.transform.html)
 - [SeriesGroupBy.transform](https://pandas.pydata.org/docs/dev/reference/api/pandas.core.groupby.SeriesGroupBy.transform.html)

Signature: `func=None, *args, other_arg=Value, **kwargs`

 - [SeriesGroupBy.agg](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.groupby.SeriesGroupBy.aggregate.html)
 - [DataFrameGroupBy.agg](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.groupby.DataFrameGroupBy.aggregate.html)
 
Signature: `func, *args, **kwargs`

 - [GroupBy.apply](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.groupby.GroupBy.apply.html)
 - [Resampler.aggregate](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.resample.Resampler.aggregate.html)
 - [Expanding.aggregate](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.window.expanding.Expanding.aggregate.html)
- [Resampler.apply](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.resample.Resampler.apply.html)

Signature: `arg, *args, **kwargs`

 - [Resampler.transform](https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.core.resample.Resampler.transform.html)