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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 read_audit_log(self, symbol=None, message=None):
 """ Return the audit log associated with a given symbol Parameters symbol : `str` symbol name for the item """

        query = {}
        if symbol:
            if isinstance(symbol, six.string_types):
                query['symbol'] = {'$regex': symbol}
            else:
                query['symbol'] = {'$in': list(symbol)}

        if message is not None:
            query['message'] = message

        def _pop_id(x):
            x.pop('_id')
            return x

        return [_pop_id(x) for x in self._audit.find(query, sort=[('_id', -1)])]