def _is_kron(tt_a):
  """Returns True if the argument is a Kronecker product matrix.

  Args:
    t_a: `TensorTrain` or `TensorTrainBatch` object.
    
  Returns:
    bool
  """
  if tt_a.is_tt_matrix():
    return max(tt_a.get_tt_ranks()) == 1
  return False