sig_def_builder.add_inputs(inputs_buf);
    sig_def_builder.add_outputs(outputs_buf);
    sig_def_builder.add_signature_key(signature_key_buf);
    sig_def_builder.add_subgraph_index(signature_def_data.subgraph_index);
    signature_defs_buffer.push_back(sig_def_builder.Finish());
    ++subgraph_index;
  }

  return builder_.CreateVector(signature_defs_buffer);
}