code: func GetBloomTrieRoot(db ethdb.Database, sectionIdx uint64, sectionHead common.Hash) common.Hash {
  	var encNumber [8]byte
  	binary.BigEndian.PutUint64(encNumber[:], sectionIdx)
  	data, _ := db.Get(append(append(bloomTriePrefix, encNumber[:]...), sectionHead.Bytes()...))
  	return common.BytesToHash(data)
  }
docs: // GetBloomTrieRoot reads the BloomTrie root assoctiated to the given section from the database