docs: def associated_parts(self, *args, **kwargs):
          """Retrieve models and instances belonging to this activity.
  
          This is a convenience method for the :func:`Activity.parts()` method, which is used to retrieve both the
          `Category.MODEL` as well as the `Category.INSTANCE` in a tuple.
  
          This call only returns the configured properties in an activity. So properties that are not configured
          are not in the returned parts.
  
          If you want to retrieve only the models associated to this task it is better to use:
              `task.parts(category=Category.MODEL)`.
  
          See :func:`pykechain.Client.parts` for additional available parameters.
  
          :returns: a tuple(models of :class:`PartSet`, instances of :class:`PartSet`)
  
          Example
          -------
          >>> task = project.activity('Specify Wheel Diameter')
          >>> all_models, all_instances = task.associated_parts()
  
          """
          return (
              self.parts(category=Category.MODEL, *args, **kwargs),
              self.parts(category=Category.INSTANCE, *args, **kwargs)
          )