for flow_name, flow in self._flows.items():
            <http://self.logger.info|self.logger.info>("Uploading flow '{}'".format(flow_name))

            data = flow_to_bytes_pickle(flow)
            if self.stored_as_script:

                # these checks are here in build() instead of the constructor
                # so that serialization and deserialization of flows doesnot fail
                if not self.flow_script_path:
                    msg = "flow_script_path must be provided if stored_as_script=True"
                    self.logger.critical(msg)
                    raise RuntimeError(msg)

                if not os.path.isfile(self.flow_script_path):
                    msg = "file '{}' passed to flow_script_path does not exist".format(
                        self.flow_script_path
                    )
                    self.logger.critical(msg)
                    raise RuntimeError(msg)

                with open(self.flow_script_path, "r") as f:
                    data = f.read().encode("utf-8")

            req_function = self._method_to_function[self.build_request_http_method]