How to use the httpstan.services.arguments function in httpstan

if len(init) != num_chains:
            raise ValueError("Initial values must be provided for each chain.")

        payloads = []
        for chain in range(1, num_chains + 1):
            payload = {"function": "stan::services::sample::hmc_nuts_diag_e_adapt"}
            payload.update(kwargs)
            payload["chain"] = chain
            payload["data"] = self.data
            payload["init"] = init.pop(0)
            if self.random_seed is not None:
                payload["random_seed"] = self.random_seed

            # fit needs to know num_samples, num_warmup, num_thin, save_warmup
            # progress bar needs to know some of these
            num_warmup = payload.get("num_warmup", arguments.lookup_default(arguments.Method["SAMPLE"], "num_warmup"))
            num_samples = payload.get(
                "num_samples", arguments.lookup_default(arguments.Method["SAMPLE"], "num_samples"),
            )
            num_thin = payload.get("num_thin", arguments.lookup_default(arguments.Method["SAMPLE"], "num_thin"))
            save_warmup = payload.get(
                "save_warmup", arguments.lookup_default(arguments.Method["SAMPLE"], "save_warmup"),
            )
            payloads.append(payload)

        def extract_protobuf_messages(fit_bytes):
            varint_decoder = google.protobuf.internal.decoder._DecodeVarint32
            next_pos, pos = 0, 0
            while pos < len(fit_bytes):
                msg = callbacks_writer_pb2.WriterMessage()
                next_pos, pos = varint_decoder(fit_bytes, pos)
                msg.ParseFromString(fit_bytes[pos : pos + next_pos])