code: function _prepareKeys(template, key) {
    return [].concat.apply([], _checkBraces(key).map(function (k) {
      return _checkEach(template, k);
    }));
  }
docs: Generate list of the 'simple' keys from the one 'composite' key with '@each' and braces-blocks
  
  @param {object} template
  @param {string} key
  @returns {string[]}
  @private