Possible inconsistencies for pulse identifiers when stored using PulseStorage

[lumip]

The dictionary interface of PusleStorage in principle allows it to store pulse under a different identifier than the one they were given on pulse construction, thus creating inconsistencies (or "hidden" renames).

[lumip]

Resolution: Storing PulseTemplates in PulseStorage under a different identifier should change their identifier in the PulseTemplate as well as in storage. Previous versions stored in PulseStorage under the old identifier should remain unchanged in this case.

[terrorfisch]

I see three possibilities:

1. Create a new object with the new identifier (maybe via a new renamed method of Serializable). The problem is that it might be unexpected that a following __getitem__ call gives you a different object.
2. Throw an error. The user should call that rename method by himself.
3. Create a Reference like thing. Maybe something like an AbstractPulseTemplate which references the other one on load.

[lumip]

The problems with 1 and 3 is that what is actually stored is different from what is input into __setitem__ so a call to __getitem__ would yield a different object which is generally not how the semantics of those methods work, so I actually don't think we should do that.
Option 2 would be the only safe option but would also make the dictionary semantics of PulseStorage obsolete, as they suggest that a user can just pick any identifier to store and PulseTemplate, while in fact, the identifier has to match the one set inside the PT..

Maybe we could consider removing the identifier field of the Serializable class and have the identifier be something that is external to all Serializables and can thus be easily changed by just reassigning the PT to a different id in storage without changing the object itself? This would mean that we couldn't use identifiers directly during sequencing but I don't think that would be a problem (we would just have to use the mapping of id's to PT objects, i.e. the PulseStorage or pulse registry dictionary, during sequencing)

[lumip]

This is currently fixed by PR #306 by introducing a method Serializable.renamed(new_identifier) which returns a copy of the original Serializable object with the given new identifier to enable explicit renames and having PulseStorage raise an error (which points to the possibility of renamed()) when attempting to store a PulseTemplate/Serializable under a different identifier than its internal one.

[terrorfisch]

Fixed as we throw an exception now.