code: function brackets(pattern, options) {
    const res = brackets.create(pattern, options);
    return res.output;
  }
docs: Parses the given POSIX character class `pattern` and returns a
  string that can be used for creating regular expressions for matching.
  
  @param {String} `pattern`
  @param {Object} `options`
  @return {Object}
  @api public