code: func (whisper *Whisper) BloomFilterTolerance() []byte {
  	val, exist := whisper.settings.Load(bloomFilterToleranceIdx)
  	if !exist || val == nil {
  		return nil
  	}
  	return val.([]byte)
  }
docs: // BloomFilterTolerance returns the bloom filter which is tolerated for a limited
  // time after new bloom was advertised to the peers. If sufficient time have elapsed
  // or no change of bloom filter have ever occurred, the return value will be the same
  // as return value of BloomFilter().