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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_watcher(self, issue, watcher):
 """Add a user to an issue's watchers list. :param issue: ID or key of the issue affected :param watcher: username of the user to add to the watchers list """

        url = self._get_url('issue/' + str(issue) + '/watchers')
        self._session.post(
            url, data=json.dumps(watcher))