def get(parent_schema_name, field_names):
        """Creates a nametuple with field_names as values. Returns an existing instance if was already created.

        :param parent_schema_name: Schema name becomes is part of the cache key
        :param field_names: defines names of the fields in the namedtuple created/returned. Also part of the cache key.
        :return: A namedtuple with field names defined by `field_names`
        """
        # Cache key is a combination of schema name and all field names
        if _UNISCHEMA_FIELD_ORDER.lower() == 'alphabetical':
            field_names = list(sorted(field_names))
        else:
            field_names = list(field_names)
        key = ' '.join([parent_schema_name] + field_names)
        if key not in _NamedtupleCache._store:
            _NamedtupleCache._store[key] = _new_gt_255_compatible_namedtuple(
                '{}_view'.format(parent_schema_name), field_names)
        return _NamedtupleCache._store[key]
Creates a nametuple with field_names as values. Returns an existing instance if was already created.

        :param parent_schema_name: Schema name becomes is part of the cache key
        :param field_names: defines names of the fields in the namedtuple created/returned. Also part of the cache key.
        :return: A namedtuple with field names defined by `field_names`
        
petastorm/unischema.py