title: Is there a way to list all available third-party plotting backends in pandas (programmatically, in Python code)?
body: <p>In Pandas, the list of available plotting backends changes and get updated over time, but is there a function/attribute to actually print them?</p>
  <p><a href="https://pandas.pydata.org/pandas-docs/stable/development/extending.html#plotting-backends" rel="nofollow noreferrer">https://pandas.pydata.org/pandas-docs/stable/development/extending.html#plotting-backends</a></p>
  <p>I understand I can query the existing one like this:</p>
  <pre><code>print(pd.options.plotting.backend)
  matplotlib
  </code></pre>
  <p>Or, for example, if I need all the templates in plotly, I can write:</p>
  <pre><code>import plotly.io as pio
  pio.templates
  </code></pre>
  <p>And then I get:</p>
  <pre><code>Default template: 'plotly'
  Available templates:
      ['ggplot2', 'seaborn', 'simple_white', 'plotly',
       'plotly_white', 'plotly_dark', 'presentation', 'xgridoff',
       'ygridoff', 'gridon', 'none']
  </code></pre>
  <p>Is is possible to get such information for the available pandas plotting backends, too?</p>