code: def get_all_child_edges(self):
          
          all_child_edges = set()
          for parent in self.children:
              all_child_edges.add((parent.item_id, self.item_id))
              all_child_edges |= parent.get_all_child_edges()
          return all_child_edges
docs: Return tuples for all child GO IDs, containing current GO ID and child GO ID.