Create Lockable mixin

[psomhorst]

It is useful if objects can be locked and considered immutable. Numpy arrays can be flagged as locked, which makes them immutable. This mixin should offer easy access to those flags. Non-arrays may be prevented from being overwritten using a custom __setattr__ method. Lists may be converted to tuples. Dicts may be converted to typing.MappingProxyType. However, locking of nested objects is not trivial.

[psomhorst]

Caching of objects requires that they can be hashed and are immutable.

Dictionaries can't be hashed or made immutable. As far as I can see, no dictionaries are used except for:

• parameters (to be replaced with new provenance tracking)
• DataCollection

This would mean that a DataCollection is not cashable, and by extension a sequence. We could create a lockable version of the DataCollection that:

• saves items in an internal list instead of a dictionary
• implements required methods to make it function as if it was a dict (iter, items, keys, etc)
• replace the list with a tuple on locking