'ImageHDU verify method.'

def _verify(self, option='warn'):

    errs = super(ImageHDU, self)._verify(option=option)
    naxis = self._header.get('NAXIS', 0)
    self.req_cards('PCOUNT', (naxis + 3), (lambda v: (_is_int(v) and (v == 0))), 0, option, errs)
    return errs
