title: autodoc_pydantic: Show fields from parent model
body: <p>I'm using the <code>autodoc_pydantic</code> plugin for Sphinx to document my <code>pydantic.BaseModel</code> classes.  However, there are cases where I have something like</p>
  <pre class="lang-py prettyprint-override"><code>class Foo(pydantic.BaseModel):
      '''Foo class'''
  
      x: str = pydantic.Field(description='The x.')
  
  class Bar(Foo):
      '''Bar class'''
  
      y: int = pydantic.Field(description='The y.')
  </code></pre>
  <p>My .rst file contains the directive</p>
  <pre><code>.. automodule:: foo.foo
      :members:
  </code></pre>
  <p>When the documentation is generated, only the <code>y</code> field is shown for the <code>Bar</code> class.  Is there a way to get <code>autodoc_pydantic</code> to show both <code>x</code> and <code>y</code> in <code>Bar</code>'s description?</p>