promql/parse.go
func parseSeriesDesc(input string) (labels.Labels, []sequenceValue, error) {
	p := newParser(input)
	p.lex.seriesDesc = true

	return p.parseSeriesDesc()
}
func parseSeriesDesc(input string) (labels.Labels, []sequenceValue, error) {
	p := newParser(input)
	p.lex.seriesDesc = true

	return p.parseSeriesDesc()
}
// parseSeriesDesc parses the description of a time series.