Compute the learning Rate for a given epoch using Stochastic Gradient Descent with Warm Restarts. Implements approach from this paper.

## Arguments

- lrmin
Lower limit of the range for the learning rate.

- lrmax
Upper limit of the range for the learning rate.

- restart
Number of epochs until a restart is conducted.

- mult
Factor, by which the number of epochs until a restart is increased at every restart.

- epoch
Epoch, for which the learning rate shall be calculated.