code: func (self *StateDB) GetStorageProof(a common.Address, key common.Hash) ([][]byte, error) {
  	var proof proofList
  	trie := self.StorageTrie(a)
  	if trie == nil {
  		return proof, errors.New("storage trie for requested address does not exist")
  	}
  	err := trie.Prove(crypto.Keccak256(key.Bytes()), 0, &proof)
  	return [][]byte(proof), err
  }
docs: // GetProof returns the StorageProof for given key