Additional Nodes functionality and Node robustness

[haavahk]

If relevant a pull request should include

• A reference to a related issue in your repository.
• A description of the changes proposed in the pull request.
• @mentions of the person or team responsible for reviewing proposed changes.
• Make sure you have made a pull of the latest changes from the main branch and re-run all unittests
• Lastly remember to lint with, isort, flake8 and black

Remember to perform linting before making a pull request

pip install black isort flake8
isort .
flake8 .
black .

[Krande]

A lot of good work here :)

Take a look at my comments when you have time and we can discuss how\if we should implement my suggested edits prior to merge

[Krande]

What about the ref on the old node referring to the element it was just deleted from?

Consider adding something like this at the end of each element eval

old_node.refs.pop(old_node.refs.index(elem))

[Krande]

Is logging error and return the right mechanism here? Obviously if a element does not contain a node which thinks it is a member of the element then something is probably very wrong.

Therefore I suggest a raise ValueError might be a better fit here stopping any further execution since this error should in principle never happen?