'Returns a single user.
The twitter.Api instance must be authenticated.
Args:
user_id:
The id of the user to retrieve.
[Optional]
screen_name:
The screen name of the user for whom to return results for. Either a
user_id or screen_name is required for this method.
[Optional]
include_entities:
if set to False, the \'entities\' node will not be included.
[Optional]
Returns:
A twitter.User instance representing that user'

def GetUser(self, user_id=None, screen_name=None, include_entities=True):

    url = ('%s/users/show.json' % self.base_url)
    parameters = {}
    if (not self._oauth_consumer):
        raise TwitterError('The    twitter.Api    instance    must    be    authenticated.')
    if user_id:
        parameters['user_id'] = user_id
    elif screen_name:
        parameters['screen_name'] = screen_name
    else:
        raise TwitterError('Specify    at    least    one    of    user_id    or    screen_name.')
    if (not include_entities):
        parameters['include_entities'] = 'false'
    json = self._FetchUrl(url, parameters=parameters)
    data = self._ParseAndCheckTwitter(json)
    return User.NewFromJsonDict(data)
