code: func ReadFastTrieProgress(db ethdb.Reader) uint64 {
  	data, _ := db.Get(fastTrieProgressKey)
  	if len(data) == 0 {
  		return 0
  	}
  	return new(big.Int).SetBytes(data).Uint64()
  }
docs: // ReadFastTrieProgress retrieves the number of tries nodes fast synced to allow
  // reporting correct numbers across restarts.