code: def get_course_completions(cls, user, course_key):
          
          user_course_completions = cls.user_course_completion_queryset(user, course_key)
          return cls.completion_by_block_key(user_course_completions)
docs: Returns a dictionary mapping BlockKeys to completion values for all
          BlockCompletion records for the given user and course_key.
  
          Return value:
              dict[BlockKey] = float