How to use the @ui5/webcomponents-base/dist/util/FocusableElements.js.getFirstFocusableElement function in @ui5/webcomponents-base

setInitialFocus(container) {
		if (this._initialFocusDomRef) {
			if (this._initialFocusDomRef !== document.activeElement) {
				this._initialFocusDomRef.focus();
			}
			return;
		}

		if (!container) {
			return;
		}

		const focusableElement = getFirstFocusableElement(container);

		if (focusableElement) {
			focusableElement.focus();
		} else {
			container.focus();
		}
	}

let focusableElement;
		let isSpecialCase = false;

		switch (target.id) {
		case `${this._id}-firstfe`:
			focusableElement = getLastFocusableElement(container);
			isSpecialCase = true;
			break;
		case `${this._id}-lastfe`:
			focusableElement = getFirstFocusableElement(container);
			isSpecialCase = true;
			break;
		case `${this._id}-blocklayer`:
			focusableElement = this._currentFocusedElement
				|| getFirstFocusableElement(container);
			isSpecialCase = true;
			break;
		}

		if (focusableElement) {
			focusableElement.focus();
		} else if (isSpecialCase) {
			container.focus();
		}

		this._currentFocusedElement = focusableElement || document.activeElement;
	}

applyInitialFocus() {
		const element = this.getRootNode().getElementById(this.initialFocus) || document.getElementById(this.initialFocus) || getFirstFocusableElement(this.contentDOM);

		if (element) {
			element.focus();
		}
	}

forwardToFirst() {
		const firstFocusable = getFirstFocusableElement(this.contentDOM);

		if (firstFocusable) {
			firstFocusable.focus();
		}
	}

let target = event.target;

		while (target.shadowRoot && target.shadowRoot.activeElement) {
			target = target.shadowRoot.activeElement;
		}

		let focusableElement;
		let isSpecialCase = false;

		switch (target.id) {
		case `${this._id}-firstfe`:
			focusableElement = getLastFocusableElement(container);
			isSpecialCase = true;
			break;
		case `${this._id}-lastfe`:
			focusableElement = getFirstFocusableElement(container);
			isSpecialCase = true;
			break;
		case `${this._id}-blocklayer`:
			focusableElement = this._currentFocusedElement
				|| getFirstFocusableElement(container);
			isSpecialCase = true;
			break;
		}

		if (focusableElement) {
			focusableElement.focus();
		} else if (isSpecialCase) {
			container.focus();
		}

		this._currentFocusedElement = focusableElement || document.activeElement;