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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 since(self, start, field=None):
 """ Add the start date to query data starting from that date sets the default start date for each query :param start: date to start looking at the fields (from date) :param field: specific field for the start date in range filter for the Search object :returns: self, which allows the method to be chainable with the other methods """


        if not field:
            field = "grimoire_creation_date"
        self.start_date = start

        date_dict = {field: {"gte": "{}".format(self.start_date.isoformat())}}
        self.search = self.search.filter("range", **date_dict)
        return self