Using Result library

[Tanguy]

You are missing the `ok` in the success path:
    
    
    proc getValue(node: ValuesNode, key: Bytes32) : Result[Bytes32, string] =
      if node.values[key[^1]] == nil:
        err("Value not found")
      else:
        ok(cast[Bytes32](node.values[key[^1]]))
    
    
    Run

(took the liberty to remove the returns, but that is not necessary)