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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 execute(self, sql, parameters=None):
 """ Execute an SQL command or query :param sql: A (unicode) string that contains the SQL command or query. If you would like to use parameters, please use a question mark ``?`` at the location where the parameter shall be inserted. :param parameters: An iterable of parameter values. The number of values must match the number of parameters in the SQL string. :return: The ``Cursor`` object to allow chaining of operations. """

        self.rowcount = -1
        self._assert_valid()
        self.impl.prepare(sql)
        if parameters:
            buffer = make_parameter_set(self.impl)
            buffer.add_set(parameters)
            buffer.flush()
        return self._execute()