<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def acquire_auth_token_ticket(self, headers=None):
        '''
        Acquire an auth token from the CAS server.
        '''
        logging.debug('[CAS] Acquiring Auth token ticket')
        url = self._get_auth_token_tickets_url()
        text = self._perform_post(url, headers=headers)
        auth_token_ticket = json.loads(text)['ticket']
        logging.debug('[CAS] Acquire Auth token ticket: {}'.format(
            auth_token_ticket))
        return auth_token_ticket