code: func (db *cachingDB) ContractCode(addrHash, codeHash common.Hash) ([]byte, error) {
  	code, err := db.db.Node(codeHash)
  	if err == nil {
  		db.codeSizeCache.Add(codeHash, len(code))
  	}
  	return code, err
  }
docs: // ContractCode retrieves a particular contract's code.