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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 user_activity_stats_by_date(self, username, date, grouped=None):
 """ Retrieve activity information about a specific user on the specified date. Params: username (string):
 filters the username of the user whose activity you are interested in. date (string):
 filters by the date of interest, best provided in ISO format: YYYY-MM-DD grouped (boolean):
 filters whether or not to group the commits Returns: list: A list of activities done by a given user on some particular date for all the projects for given Pagure instance. """

        request_url = "{}/api/0/user/{}/activity/{}".format(self.instance, username, date)

        payload = {}
        if username is not None:
            payload['username'] = username
        if date is not None:
            payload['date'] = date
        if grouped is not None:
            payload['grouped'] = grouped

        return_value = self._call_api(request_url, params=payload)

        return return_value['activities']