'Returns information about the relationship between the two users.
Args:
source_id:
The user_id of the subject user [Optional]
source_screen_name:
The screen_name of the subject user [Optional]
target_id:
The user_id of the target user [Optional]
target_screen_name:
The screen_name of the target user [Optional]
Returns:
A Twitter Json structure.'

def ShowFriendship(self, source_user_id=None, source_screen_name=None, target_user_id=None, target_screen_name=None):

    url = ('%s/friendships/show.json' % self.base_url)
    data = {}
    if source_user_id:
        data['source_user_id'] = source_user_id
    elif source_screen_name:
        data['source_screen_name'] = source_screen_name
    else:
        raise TwitterError({'message': 'Specify    at    least    one    of    source_user_id    or    source_screen_name.'})
    if target_user_id:
        data['target_user_id'] = target_user_id
    elif target_screen_name:
        data['target_screen_name'] = target_screen_name
    else:
        raise TwitterError({'message': 'Specify    at    least    one    of    target_user_id    or    target_screen_name.'})
    resp = self._RequestUrl(url, 'GET', data=data)
    data = self._ParseAndCheckTwitter(resp.content.decode('utf-8'))
    return data
