title: Import command fails when repository is used as a submodule
body: <p>Sorry, I know it's a overasked topic but I'm pretty new to these stuff and didn't understand.
  I have a repository with the following structure:</p>
  <pre><code>    repo_name/
             func_folder1/
                       func_file1.py -&gt; func_1()
             func_folder2/
                       func_file2.py -&gt; func_2()
  </code></pre>
  <p>func_2() exploits returned values of func_1() so I use the</p>
  <pre><code>    from func_folder1.func_file1 import func_1
  </code></pre>
  <p>command line inside func_file2.py to make everything work... and it works.
  Now, I have another repository &quot;repo_name2&quot; where I need many services from &quot;repo_name&quot;, so I added the latter as a submodule. Unfortunately an error arises:</p>
  <pre><code>    ModuleNotFoundError: No module named 'func_folder1'
  </code></pre>
  <p>If I change the import to</p>
  <pre><code>    from ..func_folder1.func_file1 import func_1
  </code></pre>
  <p>it works in the repo_name2 but not in the repo_name. Seems pretty annoying to change it every time. Any idea?</p>
  <p>(Python 3.9.7, Windows 10)</p>