Fix calling special Pandas plotting methods with the hvplot backend

[maximlt]

Fixes #1483

When a plotting backend is configured on pandas via e.g. pd.options.plotting.backend = '<backend>', Pandas has two ways to use it:

1. it will try to see if it is registered as an entry point and if so will load the registered module (holoviews = "hvplot:plotting" registers holoviews as an entry point pointing to the hvplot.plotting module).
2. if 1/ doesn't succeed, it will load the module as is

In both cases, the only check Pandas performs is to verify that the backend has a plot attribute.

#347 exposed the plot function from hvplot.plotting in the top-level module, allowing users to register the backend with pd.options.plotting.backend = 'hvplot' (leveraging 2/). However, that is not enough to give users access to the special plot methods Pandas expects like boxplot or hist.

This PR fixes that by adding another hvplot entry point.

[maximlt]

This is the fix.

[Azaya89]

There are multiple ways a hist plot can be plotted and some of them still don't work while the ones that work give different outputs. I checked out this branch and tried them:

Some data

import numpy as np
import pandas as pd

np.random.seed(123456)

ts = pd.Series(np.random.randn(1000), index=pd.date_range('1/1/2000', periods=1000))

1. Using hvplot.pandas works

import hvplot.pandas

ts.hvplot.hist()

Default number of bins = 20

2. Setting the plotting backend
   2a.

pd.options.plotting.backend = 'hvplot'

ts.hist()

AttributeError                            Traceback (most recent call last)
Cell In[3], line 3
      1 pd.options.plotting.backend = 'hvplot'
----> 3 ts.hist()

File ~/hvplot/.pixi/envs/default/lib/python3.12/site-packages/pandas/plotting/_core.py#line=128, in hist_series(self, by, ax, grid, xlabelsize, xrot, ylabelsize, yrot, figsize, bins, backend, legend, **kwargs)
     62 """
     63 Draw histogram of the input series using matplotlib.
     64 
   (...)
    126     >>> hist = ser.groupby(level=0).hist()
    127 """
    128 plot_backend = _get_plot_backend(backend)
--> 129 return plot_backend.hist_series(
    130     self,
    131     by=by,
    132     ax=ax,
    133     grid=grid,
    134     xlabelsize=xlabelsize,
    135     xrot=xrot,
    136     ylabelsize=ylabelsize,
    137     yrot=yrot,
    138     figsize=figsize,
    139     bins=bins,
    140     legend=legend,
    141     **kwargs,
    142 )

AttributeError: module 'hvplot' has no attribute 'hist_series'

2b. Prepending with plot works

pd.options.plotting.backend = 'hvplot'

ts.plot.hist()

Default number of bins = 10

[maximlt]

Did you re-install hvplot in your environment? I think it needs to be done for the new entry-point to be registered.

[Azaya89]

Did you re-install hvplot in your environment? I think it needs to be done for the new entry-point to be registered.

Thank you. I didn't know that.

[maximlt]

Did you re-install hvplot in your environment? I think it needs to be done for the new entry-point to be registered.

Thank you. I didn't know that.

Relieved to see it works as it's what is tested with https://github.com/holoviz/hvplot/pull/1491/files#diff-8d066bf9f51083145a38e3d3346ad7f86ac33f994b9008217f2cc92a91aa0b05R72-R77