'Summarize the HDU: name, dimensions, and formats.'

def _summary(self):

    class_name = self.__class__.__name__
    if self._data_loaded:
        if (self.data is None):
            (_shape, _format) = ((), '')
        else:
            _shape = list(self.data.shape)
            _format = self.data.dtype.name
            _shape.reverse()
            _shape = tuple(_shape)
            _format = _format[(_format.rfind('.') + 1):]
    else:
        _shape = ()
        for idx in range(self.header['NAXIS']):
            _shape += (self.header[('NAXIS' + str((idx + 1)))],)
        _format = BITPIX2DTYPE[self.header['BITPIX']]
    return (self.name, self.ver, class_name, len(self.header), _shape, _format)
