def _countblanks(self):
        """Returns the number of blank cards at the end of the Header."""

        for idx in range(1, len(self._cards)):
            if not self._cards[-idx].is_blank:
                return 1 - idx
        return 0
dataset/ETHPy150Open spacetelescope/PyFITS/pyfits/header.py/Header._countblanks/swapped operands of `-`