code: def add_children_gos(self, gos):
          
          lst = []
          obo_dag = self.obo_dag
          get_children = lambda go_obj: list(go_obj.get_all_children()) + [go_obj.id]
          for go_id in gos:
              go_obj = obo_dag[go_id]
              lst.extend(get_children(go_obj))
          return set(lst)
docs: Return children of input gos plus input gos.