code: def test_broadcast_single_kv_pair():
      """single key-value pair push & pull"""
  
      def check_single_kv_pair(kv, key):
          # single output
          ones = mx.nd.ones(shape)
          out = mx.nd.empty(shape)
          kv.broadcast(key, ones, out)
          check_diff_to_scalar(out, 1)
          # list output
          out_list = [mx.nd.empty(shape)] * 3
          key_list = key + key
          kv.broadcast(key_list, ones, out_list)
          for o in out_list:
              check_diff_to_scalar(o, 1)
  
      for name in ["device", "teststore"]:
          check_single_kv_pair(init_kv(name), 3)
          check_single_kv_pair(init_kv(name), "a")
  
file_path: mxnet/tests/python/unittest/test_kvstore_custom.py
imports: import mxnet
  import numpy
  import unittest
  from mxnet.test_utils import rand_ndarray, assert_almost_equal
  from common import assertRaises
  from mxnet.base import py_str, MXNetError
label_desc: Use image node_id 3 for calling a global function with example usage: test_broadcast_single_kv_pair() without return types