Return whether an output is considered missing or not.

def missing(self, *args, **kwds):
        """Return whether an output is considered missing or not."""
        from functools import reduce

        indexer = kwds['indexer']
        freq = kwds['freq'] or generic.default_freq(**indexer)

        miss = (checks.missing_any(generic.select_time(da, **indexer), freq) for da in args)
        return reduce(np.logical_or, miss)