'Befriends the user specified in the user parameter as the authenticating user.
The twitter.Api instance must be authenticated.
Args:
The ID or screen name of the user to befriend.
Returns:
A twitter.User instance representing the befriended user.'

def CreateFriendship(self, user):

    url = (TWITTER_API_ROOT + ('friendships/create/%s.json' % user))
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return User.NewFromJsonDict(data)
