getSeparatedKeywords(sv) {
    let stack = [];
    sv.forEach(kw => {
      if (!this.opt.separateWordSearch) {
        if (kw.trim() && stack.indexOf(kw) === -1) {
          stack.push(kw);
        }
      } else {
        kw.split(' ').forEach(kwSplitted => {
          if (kwSplitted.trim() && stack.indexOf(kwSplitted) === -1) {
            stack.push(kwSplitted);
          }
        });
      }
    });
    return {
      // sort because of https://git.io/v6USg
      'keywords': stack.sort((a, b) => {
        return b.length - a.length;
      }),
      'length': stack.length
    };
  }
Returns a list of keywords dependent on whether separate word search
was defined. Also it filters empty keywords
@param {array} sv - The array of keywords
@return {Mark~separatedKeywords}
@access protected