code: func (whisper *Whisper) BloomFilter() []byte {
  	val, exist := whisper.settings.Load(bloomFilterIdx)
  	if !exist || val == nil {
  		return nil
  	}
  	return val.([]byte)
  }
docs: // BloomFilter returns the aggregated bloom filter for all the topics of interest.
  // The nodes are required to send only messages that match the advertised bloom filter.
  // If a message does not match the bloom, it will tantamount to spam, and the peer will
  // be disconnected.