code: function sanitizeOptions(userOptions) {
      userOptions = userOptions || {};
  
      let options = {
          index: getIndexValue(userOptions)
      }
  
      if(userOptions.index){
          // required to not interfere with serve-static
          delete userOptions.index;
      }
  
      if (typeof (userOptions.enableBrotli) !== "undefined") {        
          options.enableBrotli = !!userOptions.enableBrotli;
      }
  
      if (typeof (userOptions.customCompressions) === "object" ) {
          options.customCompressions = userOptions.customCompressions;
      }
  
      if (typeof (userOptions.orderPreference) === "object" ) {
          options.orderPreference = userOptions.orderPreference;
      }
  
      return options;
  }
docs: Prepares the options object for later use. Strips away any options used for serve-static.
  Removes problematic options from the input options object.
  @param {{enableBrotli?:boolean, customCompressions?:[{encodingName:string,fileExtension:string}], indexFromEmptyFile?:boolean, index?: boolean}} userOptions