Arr is returned as a matrix type, which may not be an iterable object that plays nicely with join .
In numpy, slices of matrices are matrices (note the double braces in your example). An easy way around this is to get the array representation using the . A attribute.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.