'If the data is unsigned int 16, 32, or 64 add BSCALE/BZERO cards to
header.'

def _update_uint_scale_keywords(self):

    if (self._has_data and self._standard and _is_pseudo_unsigned(self.data.dtype)):
        if ('TFIELDS' in self._header):
            self._header.set('BSCALE', 1, after='TFIELDS')
        elif ('GCOUNT' in self._header):
            self._header.set('BSCALE', 1, after='GCOUNT')
        else:
            self._header.set('BSCALE', 1)
        self._header.set('BZERO', _unsigned_zero(self.data.dtype), after='BSCALE')
