TimeSeries of values.

def values(self):
        """
        TimeSeries of values.
        """
        # if accessing and stale - update first
        if self._needupdate or self.now != self.parent.now:
            self.update(self.root.now)
        if self.root.stale:
            self.root.update(self.root.now, None)
        return self._values.loc[:self.now]