'Updates the contacts that are used for this message.
:param um_to_user_list:
List of Django :class:`User`.
:return:
A boolean if a user is contact is updated.'

def update_contacts(self, um_to_user_list):

    updated = False
    for user in um_to_user_list:
        MessageContact.objects.update_contact(self.sender, user, self)
        updated = True
    return updated
