why you use these three numbers?

[Perfeee]

In aae_pytorch_basic.py, line 181 and line 212, those three constants are used for what? and how do you choose those? BTW, please forgive my poor english.... Thank you in advance.

[fducau]

Line 181 is to normalize the input images.
Line 212 there is a constant 5 used to get samples from a normal distribution with standard deviation equal to 5.