code: func bloomBitsKey(bit uint, section uint64, hash common.Hash) []byte {
  	key := append(append(bloomBitsPrefix, make([]byte, 10)...), hash.Bytes()...)
  
  	binary.BigEndian.PutUint16(key[1:], uint16(bit))
  	binary.BigEndian.PutUint64(key[3:], section)
  
  	return key
  }
docs: // bloomBitsKey = bloomBitsPrefix + bit (uint16 big endian) + section (uint64 big endian) + hash