def fill_missing(self, value=np.nan):
        r"""Replace missing value to "value".

        Parameters:
            value: value that missing value is replaced

        Returns:
            Result

        """
        return self.__class__(
            self.mol,
            [(value if is_missing(v) else v) for v in self.values()],
            self.keys(),
        )
r"""Replace missing value to "value".

        Parameters:
            value: value that missing value is replaced

        Returns:
            Result