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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def setup(app):
 """Sphinx extension setup function When the extension is loaded, Sphinx imports this module and executes the ``setup()`` function, which in turn notifies Sphinx of everything the extension offers. Parameters app : sphinx.application.Sphinx Application object representing the Sphinx process Notes ----- This function uses the setup function of the :mod:`sphinx.ext.napoleon` module"""

    from sphinx.application import Sphinx
    if not isinstance(app, Sphinx):
        return  # probably called by tests

    app.connect('autodoc-process-docstring', process_docstring)
    return napoleon_setup(app)