def result_is_file(self):
        wrapper = self.wsgi_file_wrapper
        return wrapper is not None and isinstance(self.result,wrapper)
True if 'self.result' is an instance of 'self.wsgi_file_wrapper'
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.2/django/core/servers/basehttp.py/ServerHandler.result_is_file