presto-iceberg/src/main/java/io/prestosql/plugin/iceberg/PartitionFields.java/PartitionFields/toPartitionFields
class PartitionFields:    public static List<String> toPartitionFields(PartitionSpec spec)
    {
        return spec.fields().stream()
                .map(field -> toPartitionField(spec, field))
                .collect(toImmutableList());
    }