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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def authenticate(self, request):
 """Authenticate the user, requiring a logged-in account and CSRF. This is exactly the same as the `SessionAuthentication` implementation, with the `user.is_active` check removed. Args: request (HttpRequest) Returns: Tuple of `(user, token)` Raises: PermissionDenied: The CSRF token check failed. """

        # Get the underlying HttpRequest object
        request = request._request  # pylint: disable=protected-access
        user = getattr(request, 'user', None)

        # Unauthenticated, CSRF validation not required
        # This is where regular `SessionAuthentication` checks that the user is active.
        # We have removed that check in this implementation.
        # But we added a check to prevent anonymous users since we require a logged-in account.
        if not user or user.is_anonymous:
            return None

        self.enforce_csrf(request)

        # CSRF passed with authenticated user
        return (user, None)