code: function _classForDocument(doc) {
          switch (doc.getLanguage().getId()) {
          case "less":
          case "scss":
              return CSSPreprocessorDocument;
          case "css":
              return CSSDocument;
          case "javascript":
              return exports.config.experimental ? JSDocument : null;
          }
  
          if (LiveDevelopmentUtils.isHtmlFileExt(doc.file.fullPath)) {
              return HTMLDocument;
          }
  
          return null;
      }
docs: Determine which document class should be used for a given document
  @param {Document} document