[FEATURE] Loss Masking

[OmaymaMahjoub]

Feature

Add a feature of death masking by masking the loss so that we have 3 options when we use SMAC:

1. Without death masking
2. Death masking by masking the observation
3. Death masking by masking the loss

Proposal

Investigate if death masking by masking the loss is more effecient

Definition of done

Implement loss masking in the network and training component