'Add an LD to specified LD Set.'

def addldsetld(self, ldset, ldname, lun=None):

    if (lun is None):
        cmd = ('iSMcfg    addldsetld    -ldset    %(ldset)s    -ldname    %(ldname)s' % {'ldset': ldset, 'ldname': ldname})
        self._execute(cmd)
    else:
        cmd = ('iSMcfg    addldsetld    -ldset    %(ldset)s    -ldname    %(ldname)s    -lun    %(lun)d' % {'ldset': ldset, 'ldname': ldname, 'lun': lun})
        self._execute(cmd)
