code: def _testScope(self, factory, prefix="prefix", use_outer_scope=True):
      # REMARKS: factory(scope) is a function accepting a scope
      #          as an argument, such scope can be None, a string
      #          or a VariableScope instance.
      with self.session(use_gpu=True, graph=tf.Graph()):
          if use_outer_scope:
              with tf.variable_scope(prefix) as scope:
                  factory(scope)
          else:
              factory(prefix)
  
          # check that all the variables names starts with the proper scope.
          tf.global_variables_initializer()
          all_vars = tf.global_variables()
          prefix = prefix or "stack_bidirectional_rnn"
          scope_vars = [
              v for v in all_vars if v.name.startswith(prefix + "/")
          ]
          tf.logging.info(
              "StackRNN with scope: %s (%s)"
              % (prefix, "scope" if use_outer_scope else "str")
          )
          for v in scope_vars:
              tf.logging.info(v.name)
          self.assertEqual(len(scope_vars), len(all_vars))
  
imports: import itertools
  from absl.testing import parameterized
  from magenta.contrib import rnn
  import numpy
  import tensorflow.compat.v1
label_desc: Use image node_id 6 for calling the StackBidirectionalRNNTest obj's underlying member method code with example usage: obj._testScope(factory, prefix, use_outer_scope) without return types