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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 _flatten(self, iterator, **filter_options):
        '''
        iterator here gives as lists of tuples. Method flattens the structure
        to a single list of tuples.
        '''
        resp = list()
        for entry in iterator:
            for tup in entry:
                if self._matches_filter(tup, **filter_options):
                    resp.append(tup)
        return resp