RFE: deregister attributes

[Tom Goddard]

My mutation structure coloring code currently registers a Residue attribute called "mutation_score". Later the user may rename this. Then they may create a new attribute named "mutation_score". Only the attribute value type may be float the first time and int the second time. That gives an error. Is there a way when the user renames the attribute for me to deregister the attribute name? Or can I reregister changing float to int without an error? I did not see a way to do it.

[Eric Pettersen]

Added attribute deregistration and renaming methods (deregister_attr and rename_attr. The renaming method only moves the meta-information about the attributes -- it does not move/rename the attribute name/value pair in individual class instances.

[Tom Goddard]

It is not too convenient to use this deregister_attr() routine since my code does not keep track of which attributes it has registered. It would be nice if I can deregister an attribute without getting an error if it is already deregistered. Maybe it could have a keyword argument error_if_not_registered = True.