set containingElem(val) {
    if (!(val instanceof HTMLElement)) {
      return;
    }
    if (this.#containingElem !== val) {
      this.#containingElem = val;
      this.place();
    }
  }
/**
   * @param {HTMLElement} val an element that will appear to "contain" the Popup
   */
@param {HTMLElement} val an element that will appear to "contain" the Popup
@param { HTMLElement } val an element that will appear to " contain " the Popup
set containingElem(val) {
    if (!(val instanceof HTMLElement)) {
      return;
    }
    if (this.#containingElem !== val) {
      this.#containingElem = val;
      this.place();
    }
  }
set containingElem ( val ) { if ( ! ( val instanceof HTMLElement ) ) { return ; } if ( this . #containingElem !== val ) { this . #containingElem = val ; this . place ( ) ; } }
@param {HTMLElement} val an element that will appear to "contain" the Popup
@param { HTMLElement } val an element that will appear to " contain " the Popup