code: func ParseOpenCV(r io.Reader) (cascade *Cascade, name string, err error) {
  	// BUG(crawshaw): tag-based parsing doesn't seem to work with <_>
  	buf, err := ioutil.ReadAll(r)
  	if err != nil {
  		return
  	}
  	buf = bytes.Replace(buf, []byte("<_>"), []byte("<grp>"), -1)
  	buf = bytes.Replace(buf, []byte("</_>"), []byte("</grp>"), -1)
  
  	s := &opencv_storage{}
  	err = xml.Unmarshal(buf, s)
  	if err != nil {
  		return
  	}
  	return buildCascade(s)
  }
docs: // ParseOpenCV produces a detection Cascade from an OpenCV XML file.