code: def write_edge_features(edge_features, edge_file):
      """
      Utility function to serialize edge_features in edge_file file
  
      Parameters:
      -----------
      edge_features : dictionary
          dictionary storing etype <-> list of features
      edge_file     : string
          File in which the edge information is serialized
      """
      dgl.data.utils.save_tensors(edge_file, edge_features)
  
imports: import json
  import logging
  import os
  from itertools import cycle
  import constants
  import dgl
  import numpy
  import psutil
  import pyarrow
  import torch
  from dgl.distributed.partition import _dump_part_config
  from pyarrow import csv
label_desc: Use image node_id 15 for calling a global function with example usage: write_edge_features(edge_features, edge_file) without return types