def METHOD_NAME(shelf, left, right, pivot_index):
    pivot = shelf[pivot_index]
    shelf.insert(right, shelf.pop(pivot_index))
    store_index = left
    for i in range(left, right): # range is non-inclusive of ending value
        if shelf[i].size < pivot.size:
            shelf.insert(store_index, shelf.pop(i))
            store_index = store_index + 1
    shelf.insert(store_index, shelf.pop(right)) # move pivot to correct position
    return store_index