code: def extend_schema_spec(self) -> None:
          
          super().extend_schema_spec()
  
          identity_field = {
              'Name': '_identity',
              'Type': BtsType.STRING,
              'Value': 'identity',
              ATTRIBUTE_INTERNAL: True
          }
  
          if self.ATTRIBUTE_FIELDS in self._spec:
              self._spec[self.ATTRIBUTE_FIELDS].insert(0, identity_field)
              self.schema_loader.add_schema_spec(identity_field, self.fully_qualified_name)
docs: Injects the identity field