code: def _make_variable(self, metric, value):
      with tf.name_scope("MetricAverageCallback") as scope:
          var = tf.Variable(value, name=metric)
          self.backend.get_session().run(var.initializer)
          push_pull_op = bps.push_pull(
              var, scope, device_dense=self.device
          )
          return var, push_pull_op
  
imports: import warnings
  import byteps.tensorflow
  import tensorflow
label_desc: Use image node_id 2 for calling the MetricAverageCallbackImpl obj's underlying member method code with example usage: obj._make_variable(metric, value) and returns: var,  push_pull_op