'fetch cached blocks for course - retain for subsequent use'

def get_course_blocks(self, user):

    course_key = self.get_course_key()
    if (course_key not in self._course_blocks):
        root_block_usage_key = self.get_module_store().make_course_usage_key(course_key)
        self._course_blocks[course_key] = get_course_blocks(user, root_block_usage_key)
    return self._course_blocks[course_key]
