<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def values(self, *keys):
 """ Return the values of the record, optionally filtering to include only certain values by index or key. :param keys: indexes or keys of the items to include; if none are provided, all values will be included :return: list of values """

        if keys:
            d = []
            for key in keys:
                try:
                    i = self.index(key)
                except KeyError:
                    d.append(None)
                else:
                    d.append(self[i])
            return d
        return list(self)