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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 filter(self):
 """Generate a filtered query from request parameters. :returns: Filtered SQLALchemy query """

        argmap = {
            filter.label or label: filter.field
            for label, filter in self.filters.items()
        }
        args = self.opts.parser.parse(argmap)
        query = self.query if self.query is not None else self.opts.query
        for label, filter in self.filters.items():
            value = args.get(filter.label or label)
            if value is not None:
                query = filter.filter(query, self.opts.model, label, value)
        return query