'This field contains an identifier that indicates the LIS Result Identifier (if any)
associated with this launch.  This field identifies a unique row and column within the
TC gradebook.  This field is unique for every combination of context_id / resource_link_id / user_id.
This value may change for a particular resource_link_id / user_id  from one launch to the next.
The TP should only retain the most recent value for this field for a particular resource_link_id / user_id.
This field is generally optional, but is required for grading.'

def get_lis_result_sourcedid(self):

    return '{context}:{resource_link}:{user_id}'.format(context=urllib.quote(self.context_id), resource_link=self.get_resource_link_id(), user_id=self.get_user_id())
