def fixed_lr(global_step, learning_rate):
  """Fixed learning rate policy.
  This function always returns ``learning_rate``, ignoring ``global_step``
  value.

  Args:
    global_step: global step TensorFlow tensor (ignored for this policy).
    learning_rate (float): fixed learning rate to use.

  Returns:
    learning rate at step ``global_step``.
  """
  return learning_rate