使用内置的issubclass方法判断类之间是否存在继承关系

# 可以使用python内置的issubclass方法来判断两个类之间是否存在继承关系

>>> class BaseClass: pass
>>> class SubClass(BaseClass): pass

>>> issubclass(SubClass, BaseClass)
True

>>> issubclass(SubClass, object)
True

>>> issubclass(BaseClass, SubClass)
False