Tests fail for some metrics due to mismatch between tensor devices

[denproc]

Describe the bug Following tests fail when GPU is used.

• test_examples.py
• test_gmsd.py
• test_ms_ssim.py
• test_ssim.py

To Reproduce Steps to reproduce the behavior:

1. Clone Repo to machine with CUDA
2. Run pytest tests
3. Observe errors

Expected behavior No errors.

Screenshots

Additional context Related to #362