code: def to_dict(self, img_coll):
          
          # Get the basic Json object from the super class
          json_obj = super(DefaultImageGroupManager, self).to_dict(img_coll)
          # Add list of images as Json array
          images = []
          for img_group in img_coll.images:
              images.append({
                  'identifier' : img_group.identifier,
                  'folder' : img_group.folder,
                  'name' : img_group.name
              })
          json_obj['images'] = images
          # Transform dictionary of options into list of elements, one per typed
          # attribute in the options set.
          json_obj['options'] = attribute.attributes_to_dict(img_coll.options)
          return json_obj
docs: Create a Json-like dictionary for image group. Extends the basic
          object with an array of image identifiers.
  
          Parameters
          ----------
          img_coll : ImageGroupHandle
  
          Returns
          -------
          (JSON)
              Json-like object, i.e., dictionary.