class_docstr: Tests for DebugIdentityV2Op: when DebugEventsWriter is initialized.
  
  DebugEventsWriter being initialized prior to DebugIdentityV2 ops being invoked
  for the first time is the typical case (e.g., tfdbg2 running on a local
  machine with only local devices.)
class_docstr_tok: ["Tests","for","DebugIdentityV2Op",":","when","DebugEventsWriter","is","initialized",".","DebugEventsWriter","being","initialized","prior","to","DebugIdentityV2","ops","being","invoked","for","the","first","time","is","the","typical","case","(","e.g.",",","tfdbg2","running","on","a","local","machine","with","only","local","devices",".",")"]
code: def testControlFlow(self):
      @def_function.function
      def collatz(x):
          counter = constant_op.constant(0, dtype=dtypes.int32)
          while math_ops.greater(x, 1):
              counter = counter + 1
              gen_debug_ops.debug_identity_v2(
                  x,
                  tfdbg_context_id="deadbeaf",
                  op_name="x",
                  output_slot=0,
                  tensor_debug_mode=debug_event_pb2.TensorDebugMode.FULL_TENSOR,
                  debug_urls=["file://%s" % self.dump_root],
              )
              if math_ops.equal(x % 2, 0):
                  x = math_ops.div(x, 2)
              else:
                  x = x * 3 + 1
          return counter
  
      x = constant_op.constant(10, dtype=dtypes.int32)
      self.evaluate(collatz(x))
  
      self.writer.FlushExecutionFiles()
      with debug_events_reader.DebugEventsReader(
          self.dump_root
      ) as reader:
          graph_trace_iter = reader.graph_execution_traces_iterators()[
              0
          ]
          try:
              x_values = []
              timestamp = 0
              while True:
                  debug_event = next(graph_trace_iter).debug_event
                  self.assertGreater(debug_event.wall_time, timestamp)
                  timestamp = debug_event.wall_time
                  trace = debug_event.graph_execution_trace
                  self.assertEqual(trace.tfdbg_context_id, "deadbeaf")
                  self.assertEqual(trace.op_name, "x")
                  self.assertEqual(trace.output_slot, 0)
                  self.assertEqual(
                      trace.tensor_debug_mode,
                      debug_event_pb2.TensorDebugMode.FULL_TENSOR,
                  )
                  x_values.append(
                      int(tensor_util.MakeNdarray(trace.tensor_proto))
                  )
          except StopIteration:
              pass
  
          # Due to the circular buffer, only the last 4 iterations of
          # [10, 5, 16, 8, 4, 2] should have been written.
          self.assertAllEqual(x_values, [16, 8, 4, 2])
  
imports: import os
  import numpy
  from tensorflow.core.protobuf import debug_event_pb2
  from tensorflow.python.debug.lib import debug_events_reader
  from tensorflow.python.debug.lib import debug_events_writer
  from tensorflow.python.debug.lib import dumping_callback_test_lib
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import errors_impl
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_util
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import gen_debug_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.platform import googletest
label_desc: Use image node_id 4 for calling the DebugIdentityV2OpTest obj's underlying member method code with example usage: obj.testControlFlow() and returns: counter