get _comboboxNode() {
    if (this.__comboboxNode) {
      return this.__comboboxNode;
    }
    const slot = this.querySelector('[slot="input"]');
    if (slot) {
      this.__comboboxNode = slot;
      return slot;
    }
    const slot2 = this._overlayCtrl?.contentWrapperNode.querySelector('[slot="input"]');
    if (slot2) {
      this.__comboboxNode = slot2;
      return slot2;
    }
    return null;
  }
Wrapper with combobox role for the text input that the end user controls the listbox with.
@type {HTMLElement}