如何将类输出为嵌套字典，并在其他属性为!= None时计算属性

class MyClass:
    def __init__(self, a, b, c, d):
        self.a = a
        self.b = b
        self.c = c
        self.d = d

class MyClass:
    def __init__(self, a, b, c, d):
        self.a = a
        self.b = b
        self.c = c
        self.d = d
    
    def to_dict(self):
        result = {}
        if self.a is not None:
            result['a'] = self.a
        if self.b is not None:
            result['b'] = self.b
        if self.c is not None:
            result['c'] = self.c
        if self.d is not None:
            result['d'] = self.d
        return result

my_object = MyClass(1, None, 3, 4)
my_dict = my_object.to_dict()
print(my_dict)

{'a': 1, 'c': 3, 'd': 4}