'Return info of the volume pair.'

def get_pair_info(self, ldev):

    pair_info = {}
    ldev_info = self.get_ldev_info(['sts', 'vol_attr'], '-ldev_id', ldev)
    if ((ldev_info['sts'] != NORMAL_STS) or _PAIR_ATTRS.isdisjoint(ldev_info['vol_attr'])):
        return None
    if (FULL_ATTR in ldev_info['vol_attr']):
        (pvol, svol_info) = self._get_full_copy_info(ldev)
        if (pvol is not None):
            pair_info['pvol'] = pvol
            pair_info.setdefault('svol_info', [])
            pair_info['svol_info'].extend(svol_info)
    if (THIN_ATTR in ldev_info['vol_attr']):
        (pvol, svol_info) = self._get_thin_copy_info(ldev)
        if (pvol is not None):
            pair_info['pvol'] = pvol
            pair_info.setdefault('svol_info', [])
            pair_info['svol_info'].extend(svol_info)
    return pair_info
