| Title | Type checking is too strict | 
| Status | suspended | 
| Priority | nice | 
| Assigned user | Nick Barnes | 
| Organization | Ravenbrook | 
| Description | When writing defect_tracker_* classes for a P4DTI extension, you have to return lists, dictionaries and so on when the documentation says to do so. You can't return a class of your own construction which presents a list or dictionary interface: if you do, you get assertion failures. | 
| Analysis | This is because we check types using instance(variable, type). Perhaps we should check merely that the interface we need is presented, by calling getattr(variable, methodname)? | 
| How found | inspection | 
| Evidence | None | 
| Observed in | 1.1.1 | 
| Introduced in | 1.1.0 | 
| Created by | Gareth Rees | 
| Created on | 2001-05-17 16:46:47 | 
| Last modified by | Nick Barnes | 
| Last modified on | 2018-07-05 17:27:37 | 
| History | 2001-05-17 GDR Created. 2018-07-05 NB Suspended because the P4DTI is obsolete.  |