code: func (f Uint64Vector) Get(i uint64) (val uint64, err error) {
  	b, err := f.db.Get(f.indexKey(i))
  	if err != nil {
  		if err == leveldb.ErrNotFound {
  			return 0, nil
  		}
  		return 0, err
  	}
  	return binary.BigEndian.Uint64(b), nil
  }
docs: // Get retrieves a uint64 value at index i from the database.
  // If the value is not found in the database a 0 value
  // is returned and no error.