<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def update_ticket(self, ticket_id=None, body=None):
 """Update a ticket. :param integer ticket_id: the id of the ticket to update :param string body: entry to update in the ticket """

        return self.ticket.addUpdate({'entry': body}, id=ticket_id)