def validate(self):
for field in (_field for _field in six.itervalues(self._fields) if _field.required):<EOL><INDENT>if field.get_swimlane() is None:<EOL><INDENT>raise ValidationError(self, '<STR_LIT>'.format(field.name))<EOL><DEDENT><DEDENT>
Explicitly validate field data

        Notes:
            Called automatically during save call before sending data to server

        Raises:
             ValidationError: If any fields fail validation