'Parses name server data.
Parses nameserver raw data and adds the device port wwns to the list
:returns: List -- list of device port wwn from ns info'

def _parse_ns_output(self, switch_data):

    return_list = []
    for line in switch_data:
        if (not (('    NL    ' in line) or ('    N    ' in line))):
            continue
        linesplit = line.split(';')
        if (len(linesplit) > 2):
            node_port_wwn = linesplit[2]
            return_list.append(node_port_wwn)
        else:
            msg = (_('Malformed    nameserver    string:    %s') % line)
            LOG.error(msg)
            raise exception.InvalidParameterValue(err=msg)
    return return_list
