Wrong sign in expression for \delta_3?

[wouterboomsma]

Thanks for this illustrative example of how to code a simple neural network from scratch. It has been quite useful for introducing students to neural networks. I just stumbled into one little issue: it seems to be that there is a sign mistake in the expression for delta_3 in the Python notebook:
\delta_3 = y - \hat{y}
as far as I can see, this should be:
\delta_3 = \hat{y} - y
It seems to be correct in the code. Do you agree?