def METHOD_NAME(self):
    class Node(_ast.AST):
        _fields = ('a', 'b')
    n = Node(41, b=42, c=43)
    self.assertEqual(41, n.a)
    self.assertEqual(42, n.b)
    self.assertEqual(43, n.c)
    self.assertEqual('abc', _ast.AST(f='abc').f)