orm.go
func (f *Field) RowsPrevious(rowIDOrKey interface{}) *PQLRowsQuery {
	idKey, err := formatIDKey(rowIDOrKey)
	if err != nil {
		return NewPQLRowsQuery("", f.index, err)
	}
	text := fmt.Sprintf("Rows(field='%s',previous=%s)", f.name, idKey)
	return NewPQLRowsQuery(text, f.index, nil)
}
func (f *Field) RowsPrevious(rowIDOrKey interface{}) *PQLRowsQuery {
	idKey, err := formatIDKey(rowIDOrKey)
	if err != nil {
		return NewPQLRowsQuery("", f.index, err)
	}
	text := fmt.Sprintf("Rows(field='%s',previous=%s)", f.name, idKey)
	return NewPQLRowsQuery(text, f.index, nil)
}
// RowsPrevious creates a Rows query with the given previous row ID/key