<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_user_to_group(self, username, group_name):
 """ Add given user to a group :param username: str :param group_name: str :return: Current state of the group """

        url = 'rest/api/2/group/user'
        params = {'groupname': group_name}
        data = {'name': username}

        return self.post(url, params=params, data=data)