testMapNodeList() {
    const col = getAll();
    function f(v, i, col2) {
      assertEquals(col, col2);
      assertEquals('number', typeof i);
      return v.tagName;
    }
    assertEquals('HRPPPPPPPPH1', structs.map(col, f).join(''));
  }
@suppress {missingProperties} vague return type from 'map'