code: func (f *filteredWriter) Write(p []byte) (n int, err error) {
  	if bytes.Contains(p, []byte("[DEBUG]")) || bytes.Contains(p, []byte("[INFO]")) {
  		if f.v {
  			return f.logOutput.Write(p)
  		}
  	} else {
  		return f.logOutput.Write(p)
  	}
  	return len(p), nil
  }
docs: // Write forwards the write to logOutput if verbose is true, or it doesn't
  // contain [DEBUG] or [INFO]. This implementation isn't technically correct
  // since Write could be called with only part of a log line, but I don't think
  // that actually happens, so until it becomes a problem, I don't think it's
  // worth dealing with the extra complexity. (jaffee)