code: function getProperties(filepath, { caseStyle }) {
    // if caseStyle is function, return the result of function
    if (is.function(caseStyle)) {
      const result = caseStyle(filepath);
      assert(is.array(result), `caseStyle expect an array, but got ${result}`);
      return result;
    }
    // use default camelize
    return defaultCamelize(filepath, caseStyle);
  }
docs: convert file path to an array of properties a/b/c.js => ['a', 'b', 'c']