code: function groupExists(group) {
    if (isPlatform('windows')) {
      throw new Error('Don\'t know how to check for group existence on Windows');
    } else {
      if (_.isEmpty(findGroup(group, {refresh: true, throwIfNotFound: false}))) {
        return false;
      } else {
        return true;
      }
    }
  }
docs: Check for group existence
  @function $os~groupExists
  @param {string|number} group - Groupname or group id
  @returns {boolean} - Whether the group exists or not
  @example
  // Check if group 'mysql' exists
  $os.groupExists('mysql');
  // => true