'Adds a bookmark for the block.
Arguments:
usage_key: UsageKey of the block.
Returns:
Bool indicating whether the bookmark was added.'

def set_bookmarked(self, usage_key):

    try:
        bookmark = api.create_bookmark(user=self._user, usage_key=usage_key)
    except ItemNotFoundError:
        log.error(u'Block    with    usage_id:    %s    not    found.', usage_key)
        return False
    bookmarks_cache = self._bookmarks_cache(usage_key.course_key)
    if (bookmarks_cache is not None):
        bookmarks_cache.append(bookmark)
    return True
