Sort by the values along either axis

        Wrapper around the :meth:`pandas.DataFrame.sort_values` method.

def sort_values(self, by, axis=0, ascending=True, inplace=False,
                    kind='quicksort', na_position='last'):
        """Sort by the values along either axis

        Wrapper around the :meth:`pandas.DataFrame.sort_values` method.
        """
        if inplace:
            self._frame.sort_values(
                by, axis=axis, ascending=ascending,
                inplace=inplace, kind=kind, na_position=na_position)
        else:
            new = self.__class__(self._frame.sort_values(
                by, axis=axis, ascending=ascending, inplace=inplace,
                kind=kind, na_position=na_position))
            new.metadata = self.metadata.copy()
            new._metadata = copy.deepcopy(self._metadata)
            return new