python3中怎么判断传入的参数是否是unicode
网上的教程都说使用isinstance( XXX , unicode)来判断
但是我在python3下这么使用会报name 'unicode' is not defined的错误，想看一下isinstance()是怎么实现的，传入参数的说明，结果发现isinstance的定义是下面这个样子，完全看不出想要判断unicode该传入什么参数，顺带问一下为什么python好多自带的参数都是这么定义的，def XXX(): return none，没有功能实现的代码
def isinstance(object, class_or_type_or_tuple):
""" isinstance(object, class-or-type-or-tuple) -> bool
Return whether an object is an instance of a class or of a subclass thereof.
With a type as second argument, return whether that is the object's type.
The form using a tuple, isinstance(x, (A, B, ...)), is a shortcut for
isinstance(x, A) or isinstance(x, B) or ... (etc.). """
return None回到正题，python3下该怎么判断是否unicode呢？
