code: func ReadDatabaseVersion(db ethdb.Reader) *uint64 {
  	var version uint64
  
  	enc, _ := db.Get(databaseVerisionKey)
  	if len(enc) == 0 {
  		return nil
  	}
  	if err := rlp.DecodeBytes(enc, &version); err != nil {
  		return nil
  	}
  
  	return &version
  }
docs: // ReadDatabaseVersion retrieves the version number of the database.