<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def versioning_models_registered(manager, base):
 """Return True if all versioning models have been registered."""

    declared_models = base._decl_class_registry.keys()
    return all(versioning_model_classname(manager, c) in declared_models
               for c in manager.pending_classes)