Как удалить ключ из словаря Python?

Node mergeSort(Node head) {
    if(head == null || head.next == null) {
        return head;
    }

    Node middle = middleElement(head);
    Node nextofMiddle = middle.next;
    middle.next = null;

    Node left = mergeSort(head);
    Node right = mergeSort(nextofMiddle);

    Node sortdList = merge(left, right);

    return sortdList;
}

Node merge(Node left, Node right) {
    if(left == null) {
        return right;
    }

    if(right == null) {
        return left;
    }
    Node temp = null;
    if(left.data < right.data) {
        temp = left;
        temp.next = merge(left.next, right);
    } else {
        temp = right;
        temp.next = merge(left, right.next);
    }

    return temp;
}

Node middleElement(Node head) {
    Node slow = head;
    Node fast = head;
    while (fast != null && fast.next != null && fast.next.next != null) {
        fast = fast.next.next;
        slow = slow.next;
    }
    return slow;
}