code: func getMissingFunctionSource(filename string, asm map[int]nodes, start, end int) (nodes, string) {
  	var fnodes nodes
  	for i := start; i <= end; i++ {
  		lrs := asm[i]
  		if len(lrs) == 0 {
  			continue
  		}
  		flat, cum := sumNodes(lrs)
  		fnodes = append(fnodes, &node{
  			info: nodeInfo{
  				name:   "???",
  				lineno: i,
  			},
  			flat: flat,
  			cum:  cum,
  		})
  	}
  	return fnodes, filename
  }
docs: // getMissingFunctionSource creates a dummy function body to point to
  // the source file and annotates it with the samples in asm.