code: def get_identity(self, record: Record) -> str:
          
          context = self.schema_context.context
          context.add_record(record)
          identity = self.identity.evaluate(context)
          if not identity:
              raise IdentityError('Could not determine identity using {}. Record is {}'.format(
                  self.identity.code_string, record))
          context.remove_record()
          return identity
docs: Evaluates and returns the identity as specified in the schema.
          :param record: Record which is used to determine the identity.
          :return: The evaluated identity
          :raises: IdentityError if identity cannot be determined.