code: def forward_reference(self, slot_range: str, owning_class: str) -> bool:
          
          for cname in self.schema.classes:
              if cname == owning_class:
                  return True             # Occurs on or after
              elif cname == slot_range:
                  return False            # Occurs before
          return True
docs: Determine whether slot_range is a forward reference