{
      'Topic'          => related_to_topic.where(related_item_type: 'Topic'),
      'StillImage'     => related_to_topic.where(related_item_type: 'StillImage'),
      'AudioRecording' => related_to_topic.where(related_item_type: 'AudioRecording'),
      'Video'          => related_to_topic.where(related_item_type: 'Video'),