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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, **filters):
 """ Add a filter to this query. Appends to any previous filters set. :rtype: Query """


        q = self._clone()
        for key, value in filters.items():
            filter_key = re.split('__', key)
            filter_attr = filter_key[0]
            if filter_attr not in self._valid_filter_attrs:
                raise ClientValidationError("Invalid filter attribute: %s" % key)

            # we use __ as a separator in the Python library, the APIs use '.'
            q._filters['.'.join(filter_key)].append(value)
        return q