APIView类perform_authentication方法的歧义

REST Framework的 APIView 类有个方法，方法里只有一句：request.user，这个挺有歧义的。

def perform_authentication(self, request):
    """
    Perform authentication on the incoming request.

    Note that if you override this and simply 'pass', then authentication
    will instead be performed lazily, the first time either
    `request.user` or `request.auth` is accessed.
    """
    request.user

乍一看谁知道user是个属性还是方法？是属性语法也不对，那只能是方法了。重写authenticate（）时，使用request.user 引用用户竟然触发了死循环。。

在Request类中找到了request.user方法：

class Request:
    ...
    @property
    def user(self):
        """
        Returns the user associated with the current request, as authenticated
        by the authentication classes provided to the request.
        """
        if not hasattr(self, '_user'):
            with wrap_attributeerrors():
                self._authenticate()
        return self._user