// User annotations.
	Log(ctx *traceContext, ev *trace.Event)

	// Finish indicates the end of the trace and finalizes generation.
	Finish(ctx *traceContext)
}

// runGenerator produces a trace into ctx by running the generator over the parsed trace.
func runGenerator(ctx *traceContext, g generator, parsed *parsedTrace, opts *genOpts) {
	for i := range parsed.events {
		ev := &parsed.events[i]

		switch ev.Kind() {
		case trace.EventSync: