checkType(cfi) {
    if (this.isCfiString(cfi)) {
      return "string"; // Is a range object
    } else if (cfi && typeof cfi === "object" && (Object(_utils_core__WEBPACK_IMPORTED_MODULE_0__["type"])(cfi) === "Range" || typeof cfi.startContainer != "undefined")) {
      return "range";
    } else if (cfi && typeof cfi === "object" && typeof cfi.nodeType != "undefined") {
      // || typeof cfi === "function"
      return "node";
    } else if (cfi && typeof cfi === "object" && cfi instanceof EpubCFI) {
      return "EpubCFI";
    } else {
      return false;
    }
  }
Check the type of constructor input
@private