Kernel metrics

[Kamuish]

Hi, all of the available kernels have a somewhat lacking documentation regarding the metrics that they accept. Do you have any plans for updating the documentation?

For example, in the ExpSquared Kernel you could have :
k(r^2)=exp(−r^2/(2* l^2 )

Just as a way to better understand the inputs of each kernel. If you want I can do it for some of them,