code: func PrettyTrace(w io.Writer, trace []*Event) {
  	depths := depths{}
  	for _, event := range trace {
  		depth := depths.GetOrSet(event.QueryID, event.ParentID)
  		fmt.Fprintln(w, formatEvent(event, depth))
  	}
  }
docs: // PrettyTrace pretty prints the trace to the writer.