Improved default handling

[blondon1]

Description

• using get with a default value directly in the attribute assignment simplifies the code and avoids the need for conditional checks later
• self.alpha = weights.w.get("alpha", None) # alpha is constraint >>> self.rescale = weights.w.get('rescale', torch.tensor([1.0]))
• reduce redundancy

Screenshots/videos:

Checklist:

• [x ] I have read contributing wiki page
• [x ] I have performed a self-review of my own code
• [x ] My code follows the style guidelines
• [x ] My code passes tests