Returns a FlagValue instance when needed. Internal method, to be
used in *2i() and i2*() methods.

def _fixup_val(self, x):
        """Returns a FlagValue instance when needed. Internal method, to be
used in *2i() and i2*() methods.

        """
        if isinstance(x, (list, tuple)):
            return type(x)(
                v if v is None or isinstance(v, FlagValue)
                else FlagValue(v, self.names)
                for v in x
            )
        return x if x is None or isinstance(x, FlagValue) else FlagValue(x, self.names)