message: Fix deprecation warnings of *_global_step functions.
diff: @@ -156,9 +156,9 @@ def optimize_loss(loss,
  loss = ops.convert_to_tensor(loss)
  contrib_framework.assert_scalar(loss)
  if global_step is None:
  - global_step = contrib_framework.get_global_step()
  + global_step = train.get_global_step()
  else:
  - contrib_framework.assert_global_step(global_step)
  + train.assert_global_step(global_step)
  with vs.variable_scope(name, "OptimizeLoss", [loss, global_step]):
  # Update ops take UPDATE_OPS collection if not provided.
  if update_ops is None:
  