code: def is_derived_from(self, identity: QualName, base: QualName) -> bool:
          
          try:
              bases = self.identity_adjs[identity].bases
          except KeyError:
              return False
          if base in bases:
              return True
          for ib in bases:
              if self.is_derived_from(ib, base):
                  return True
          return False
docs: Return ``True`` if `identity` is derived from `base`.