def _get_content_type(self):
    ct = self.headers.get('Content-Type')
if ct is None and not self._input_stream:
    if self.method in ('POST', 'PUT', 'PATCH'):
        if self._files:
            return 'multipart/form-data'
return 'application/x-www-form-urlencoded'
return None
Flask test_client: Тестирование запроса DELETE с данными