- a tuple (xmodule instance, instance_module, shared_module, module type).
- a tuple (xmodule instance, instance_module, shared_module, module category).
instance_module is a StudentModule specific to this module for this student
instance_module is a StudentModule specific to this module for this student
shared_module is a StudentModule specific to all modules with the same 'shared_state_key' attribute, or None if the module doesn't elect to share state
shared_module is a StudentModule specific to all modules with the same 'shared_state_key' attribute, or None if the module doesn't elect to share state