code: function list (type, filePath) {
    invariant(
      ALLOWED_LIST_TYPES.includes(type),
      `Type '${type}' is not supported by sketchtool`
    );
    return JSON.parse(sketchtoolExec(`list ${type} ${escape(filePath)}`));
  }
docs: List specific element type from given file
  @param  {string} type
  @param  {string} filePath
  @return {Object}