Add utility to configure PDHG for with explicit TGV or TV regularisation

[paskino]

Description

Add utility to configure PDHG for with explicit TGV or TV regularisation with Least Squares.

Example Usage

An example is on CIL-Demos TGV_tomography.py

Changes

• adds code to create the operators and function to configure PDHG with TGV explicit regularisation
• adds max to BlockDataContainer
• allows dot between a BlockDataContainer and a DataContainer

Testing you performed

Related issues/links

• closes #1593

Checklist

• [ ] I have performed a self-review of my code
• [x] I have added docstrings in line with the guidance in the developer guide
• [ ] I have updated the relevant documentation
• [ ] I have implemented unit tests that cover any new or modified functionality
• [ ] CHANGELOG.md has been updated with any functionality change
• [ ] Request review from all relevant developers
• [ ] Change pull request label to 'Waiting for review'

Contribution Notes

Please read and adhere to the developer guide and local patterns and conventions.

• [x] The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in CIL (the Work) under the terms and conditions of the Apache-2.0 License
• [x] I confirm that the contribution does not violate any intellectual property rights of third parties

[samdporter]

Hey all,

This still needs a few changes. Currently the BlockOperator.direct method still returns a BlockDataContainer with shape (1,1) rather than a DataContainer. I'll do a few more tests to see if there's anything else that needs doing.

Would you like me to do a PR or let you guys take care of it?

[MargaretDuff]

Hi @lauramurgatroyd - I like the style of the unit tests for explicit TV. They are comprehensive without being expensive. I have suggested a few changes to them and made some comments on the new utility file.