code: func AppendVersions(base string, versions ...VersionInfo) string {
  	if len(versions) == 0 {
  		return base
  	}
  
  	verstrs := make([]string, 0, 1+len(versions))
  	if len(base) > 0 {
  		verstrs = append(verstrs, base)
  	}
  
  	for _, v := range versions {
  		if !v.isValid() {
  			continue
  		}
  		verstrs = append(verstrs, v.Name+"/"+v.Version)
  	}
  	return strings.Join(verstrs, " ")
  }
docs: // AppendVersions converts versions to a string and appends the string to the string base.
  //
  // Each VersionInfo will be converted to a string in the format of
  // "product/version", where the "product" is get from the name field, while
  // version is get from the version field. Several pieces of version information
  // will be concatenated and separated by space.
  //
  // Example:
  // AppendVersions("base", VersionInfo{"foo", "1.0"}, VersionInfo{"bar", "2.0"})
  // results in "base foo/1.0 bar/2.0".