Method assertElement

src/utils/log.js:414–420

* Throws an error if the first argument isn't an Element * * Otherwise see `assert` for usage * * @param {*} shouldBeElement * @param {!Array|string=} opt_message The assertion message * @return {!Element} The value of shouldBeTrueish. * @closurePrimitive {asserts.matchesReturn}

(shouldBeElement, opt_message)

   * @closurePrimitive {asserts.matchesReturn}
   */
  assertElement(shouldBeElement, opt_message) {
    return assertions.assertElement(
      this.boundAssertFn_,
      shouldBeElement,
      opt_message
    );
  }

  /**
   * Throws an error if the first argument isn't a string. The string can