code: func (c *ChainIndexer) SectionHead(section uint64) common.Hash {
  	var data [8]byte
  	binary.BigEndian.PutUint64(data[:], section)
  
  	hash, _ := c.indexDb.Get(append([]byte("shead"), data[:]...))
  	if len(hash) == len(common.Hash{}) {
  		return common.BytesToHash(hash)
  	}
  	return common.Hash{}
  }
docs: // SectionHead retrieves the last block hash of a processed section from the
  // index database.