Google Apps Script wrapper for Translate API Limitations: - Doesn't return detectedSourceLanguage when called without source parameter; - Doesn't support prettyprint parameter; - Reduced error messages that return HTTP 200 status; - Doesn't support key parameter and billing ;)

Translate.gs

function doGet(r) {
  var translations = [];
  var e = {error:{code:400}};
  try {
    if(r.parameters.q) {
      for(var n in r.parameters.q) {        
        translations.push({translatedText:
                           LanguageApp.translate(
                             r.parameters.q[n],
                             (r.parameters.source)?r.parameters.source:null,
                             r.parameters.target,
                             {contentType: (r.parameters.format=="text")?"text":"html"}
                           )
                          });
        var response = Utilities.jsonStringify({data:{translations:translations}});
        if(r.parameters.callback) {
          if((/^[$A-Z_][0-9A-Z_$]*$/i).test(r.parameters.callback))
            response = r.parameters.callback+"("+response+");";
          else throw new Error("Invalid value for parameter callback: "+r.parameters.callback);
        }
      }
    }
    else throw new Error("Required parameter: q");
  }
  catch(err) {
    e.error.message = err.message;
    response = Utilities.jsonStringify(e);
  }
  return ContentService.createTextOutput(response).setMimeType(ContentService.MimeType.JSON);
}

from where does the LanguageApp class comes from?