def METHOD_NAME(s, expected=None):
  # type: (str, Optional[str]) -> arith_expr_t
  """Used by tests."""
  p = MakeParser(s)
  tree = p.Parse()
  sexpr = repr(tree)
  if expected is not None:
    assert sexpr == expected, '%r != %r' % (sexpr, expected)
  #print('%-40s %s' % (s, sexpr))
  return tree