:bug: Fixes:
1. SparseMultivariateNormal Initialisation Warning: Addressed a user warning emerging from the SparseMultivariateNormal class initialisation due to arg_constraints not being defined.
2. Enhancements to PairwiseVoxelEncoder:
- Module Inheritance: Adjusted PairwiseVoxelEncoder to inherit from torch.nn.Module, aligning it more closely with PyTorch's expected behavior for neural network modules.
- Device Management: Implemented the _apply function in PairwiseVoxelEncoder. This change facilitates the movement of indices created during class initialization to a designated device using methods such as .to(device), .cpu(), or .cuda().
- Device Property: Introduced the .device attribute for PairwiseVoxelEncoder. This property provides users with insights regarding the device to which the encoder's indices are assigned.
Note: v.0.1.1 was abandoned due to a code typo error (arg_contraints instead of arg_constraints)