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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 import_module(module_name):
 """ Imports a module. A single point of truth for importing modules to be documented by `pydoc`. In particular, it makes sure that the top module in `module_name` can be imported by using only the paths in `pydoc.import_path`. If a module has already been imported, then its corresponding entry in `sys.modules` is returned. This means that modules that have changed on disk cannot be re-imported in the same process and have its documentation updated. """

    if import_path != sys.path:
        # Such a kludge. Only restrict imports if the `import_path` has
        # been changed. We don't want to always restrict imports, since
        # providing a path to `imp.find_module` stops it from searching
        # in special locations for built ins or frozen modules.
        #
        # The problem here is that this relies on the `sys.path` not being
        # independently changed since the initialization of this module.
        # If it is changed, then some packages may fail.
        #
        # Any other options available?

        # Raises an exception if the parent module cannot be imported.
        # This hopefully ensures that we only explicitly import modules
        # contained in `pydoc.import_path`.
        imp.find_module(module_name.split('.')[0], import_path)

    if module_name in sys.modules:
        return sys.modules[module_name]
    else:
        __import__(module_name)
        return sys.modules[module_name]