docs: def to_dict(self, experiment):
          """Create a Json-like object for an experiment. Extends the basic
          object with subject, image group, and (optional) functional data
          identifiers.
  
          Parameters
          ----------
          experiment : ExperimentHandle
  
          Returns
          -------
          Json Object
              Json-like object, i.e., dictionary.
          """
          # Get the basic Json object from the super class
          json_obj = super(DefaultExperimentManager, self).to_dict(experiment)
          # Add associated object references
          json_obj['subject'] = experiment.subject_id
          json_obj['images'] = experiment.image_group_id
          if not experiment.fmri_data_id is None:
              json_obj['fmri'] = experiment.fmri_data_id
          return json_obj