def unassign(self, institute, case, user, link):
LOG.info("<STR_LIT>".format(<EOL>user['<STR_LIT:name>'], case['<STR_LIT>']))<EOL>self.create_event(<EOL>institute=institute,<EOL>case=case,<EOL>user=user,<EOL>link=link,<EOL>category='<STR_LIT>',<EOL>verb='<STR_LIT>',<EOL>subject=case['<STR_LIT>']<EOL>)<EOL>LOG.info("<STR_LIT>".format(<EOL>case['<STR_LIT>'], user['<STR_LIT:name>']))<EOL>updated_case = self.case_collection.find_one_and_update(<EOL>{'<STR_LIT>': case['<STR_LIT>']},<EOL>{'<STR_LIT>': {'<STR_LIT>': user['<STR_LIT>']}},<EOL>return_document=pymongo.ReturnDocument.AFTER<EOL>)<EOL>LOG.debug("<STR_LIT>")<EOL>return updated_case<EOL>
Unassign a user from a case.

        This function will create an Event to log that a person has been
        unassigned from a case. Also the user will be removed from case
        "assignees".

        Arguments:
            institute (dict): A Institute object
            case (dict): A Case object
            user (dict): A User object (Should this be a user id?)
            link (dict): The url to be used in the event

        Returns:
            updated_case (dict): The updated case