code: def get_extensions_assigned_to_user(self, user_id):
          
          route_values = {}
          if user_id is not None:
              route_values['userId'] = self._serialize.url('user_id', user_id, 'str')
          response = self._send(http_method='GET',
                                location_id='8cec75ea-044f-4245-ab0d-a82dafcc85ea',
                                version='5.0-preview.1',
                                route_values=route_values)
          return self._deserialize('{LicensingSource}', self._unwrap_collection(response))
docs: GetExtensionsAssignedToUser.
          [Preview API] Returns extensions that are currently assigned to the user in the account
          :param str user_id: The user's identity id.
          :rtype: {LicensingSource}