def get_optimizer_variables(optimizer):
  """Returns a list of variables for the given `tf.compat.v1.train.Optimizer`.

  Equivalent to `optimizer.variables()`.

  Args:
    optimizer: An instance of `tf.compat.v1.train.Optimizer` which has created
      variables (typically after a call to `Optimizer.minimize`).

  Returns:
    A list of variables which have been created by the `Optimizer`.
  """
  return optimizer.variables()