Support unsafe casting in Delta filter

[ehgus]

[Description of PR]

This is a fix of #653. The change enable unsafe casting in Delta filter. In addition, unit tests are added to catch such bug next.

TODO:

• [x] Unit tests and/or doctests in docstrings
• [x] Tests pass locally
• [x] Docstrings and API docs for any new/modified user-facing classes and functions
• [ ] Changes documented in docs/release.rst
• [x] Docs build locally
• [x] GitHub Actions CI passes
• [x] Test coverage to 100% (Codecov passes)