void * List_set(List * self, size_t index, void * value) {

    if (self == NULL) {
        assert(self != NULL && "Rewriting empty list");
        fprintf(stderr, "Rewriting empty list");
        return NULL;
    }
    int i = 0;
    SLNode * cur = self->head;
    while (i != index && cur->next != NULL) {
        i++;
        cur = cur->next;
    }
    if (i != index) {
        assert(i == index && "Invalid index");
        fprintf(stderr, "Invalid index");
        return NULL;
    }
    void * answer = cur->value;
    cur->value = value;
    return answer;
}