'Add wwns to a host if one or more don\'t exist.
Identify if argument wwns contains any world wide names
not configured in the 3PAR host path. If any are found,
add them to the 3PAR host.'

def _add_new_wwn_to_host(self, common, host, wwns):

    host_wwns = []
    if ('FCPaths' in host):
        for path in host['FCPaths']:
            wwn = path.get('wwn', None)
            if (wwn is not None):
                host_wwns.append(wwn.lower())
    compare_wwns = [x.lower() for x in wwns]
    new_wwns = list(set(compare_wwns).difference(host_wwns))
    if (len(new_wwns) > 0):
        self._modify_3par_fibrechan_host(common, host['name'], new_wwns)
        host = common._get_3par_host(host['name'])
    return host
