Examples on N-D arrays usage
There are so many examples... The way you are trying to represent it is probably wrong, let's take a simple example:

You have boxes and a box stores N items in it. You can store up to 100 items in each box.
You've organized the boxes in shelves. A shelf allows you to store M boxes. You can identify each box by a index.
All the shelves are in a warehouse with 3 floors. So you can identify any shelf using 3 numbers: the row, the column and the floor.

A box is then identified by: row, column, floor and the index in the shelf.
An item is identified by: row, column, floor, index in shelf, index in box.
Basically, one way (not the best one...) to model this problem would be to use a 5D array.
I was surprised when I started learning numpy that there are N dimensional arrays. I'm a programmer and all I thought that nobody ever use more than 2D array. Actually I can't even think beyond a 2D array. I don't know how think about 3D, 4D, 5D arrays or more. I don't know where to use them.
Can you please give me examples of where 3D, 4D, 5D ... etc arrays are used? And if one used  numpy.sum(array, axis=5) for a 5D array would what happen?