code: func (a Sources) String() string {
  	var buf bytes.Buffer
  
  	ubound := len(a) - 1
  	for i, src := range a {
  		_, _ = buf.WriteString(src.String())
  		if i < ubound {
  			_, _ = buf.WriteString(", ")
  		}
  	}
  
  	return buf.String()
  }
docs: // String returns a string representation of a Sources array.