message: Compare functions by id instead of equality
diff: @@ -81,7 +81,7 @@ def isnamedtuple(f):
  def isbuiltin(f):
  """Returns True if the argument is a built-in function."""
  - if f in six.moves.builtins.__dict__.values():
  + if any(f is builtin for builtin in six.moves.builtins.__dict__.values()):
  return True
  elif isinstance(f, types.BuiltinFunctionType):
  return True
  