code: async function() {
        if (!this.__mtime) {
          return this.read(); 
        }
        var poFile = this.getPoFilename();
        let stat = await qx.tool.compiler.files.Utils.safeStat(poFile);
        if (stat && this.__mtime == stat.mtime) {
          return undefined;
        }
        return this.read();
      }
docs: Reads the .po file, but only if it has not been loaded or has changed
  
  @returns {Promise}|