title: Sphinx with autodoc "duplicate object description" Warning when grouping members into separate files
body: <p>I have some functions in a module which I would like to break up into two groups in my documentation. I have three files:</p>
  
  <p><strong>my_mod.rst</strong></p>
  
  <pre><code>my_mod
  ======
  .. automodule:: my_mod
     :no-members:
  
  .. toctree::
     :maxdepth: 1
  
     my_mod/group1
     my_mod/group2
  </code></pre>
  
  <p><strong>group1.rst</strong></p>
  
  <pre><code>group1
  ======
  
  .. automodule:: my_mod
     :members: add, subtract
  </code></pre>
  
  <p><strong>group2.rst</strong></p>
  
  <pre><code>group2
  ======
  
  .. automodule:: my_mod
     :members: multiply, divide
  </code></pre>
  
  <p>I have to use <code>.. automodule:: my_mod</code> in each. In <code>my_mod.rst</code> so it displays the module docstring and in the other files to identify the <code>:members:</code> that I want to be displayed. However, this causes multiple errors when generating the HTML files, like:</p>
  
  <pre><code>/pathto/my_mymod.rst:2: WARNING: duplicate object description of my_mod, other instance in my_mod/group1, use :noindex: for one of them
  </code></pre>
  
  <p>If I add <code>:noindex:</code> though, I can no longer link to these functions from elsewhere in the documentation so that is not a solution for me.   </p>
  
  <p>Can I avoid these error messages without losing any functionality? Also, this seems to be working as I hoped (except for the error messages), but are there any potential pitfalls to referencing the same module multiple times?</p>