Reference Issues/PRs

Follows from #28678 (comment)

What does this implement/fix? Explain your changes.

Adds flexibe_types:

• dictionary allowing you to specify flexible types for individual param/attr/return
• allows you to specify the number of types that should be common between objects
• also remove default type checking, if you wish to only use this set int to 0

Added a very simple test case just to demonstrate its use, but no unit tests.

Any other comments?

The addition is probably more complicated than I would like, both the parameter use and the code. I do think it does address most (all?) of the type cases we would encounter though.

Not 100% and open to suggestions. Potentially a simple ignore_type option may be easier?

Note this is a draft PR, as it is just to see if we like the addition.

cc @glemaitre @adrinjalali @StefanieSenger