code: def create_used_relation(self, activity_id, entity_kind, entity_id):
          
          return self._create_activity_relation(activity_id, entity_kind, entity_id, ActivityRelationTypes.USED)
docs: Create a was used by relationship between an activity and a entity(file).
          :param activity_id: str: uuid of the activity
          :param entity_kind: str: kind of entity('dds-file')
          :param entity_id: str: uuid of the entity
          :return: requests.Response containing the successful result