code: def derived_from_all(self, identities: List[QualName]) -> MutableSet[QualName]:
          
          if not identities:
              return set()
          res = self.derived_from(identities[0])
          for id in identities[1:]:
              res &= self.derived_from(id)
          return res
docs: Return list of identities transitively derived from all `identity`.