code: func (cf *Filter) Lookup(data []byte) bool {
  	i1, i2, fp := getIndicesAndFingerprint(data, uint(len(cf.buckets)))
  	b1, b2 := cf.buckets[i1], cf.buckets[i2]
  	return b1.getFingerprintIndex(fp) > -1 || b2.getFingerprintIndex(fp) > -1
  }
docs: // Lookup returns true if data is in the counter