Access array field in lambda custom field

Given the following schema:

interface ITransactor {
    objectiveID: ID!
    incomingTransactions: [Transaction!] @hasInverse(field: to)
    outgoingTransactions: [Transaction!] @hasInverse(field: from)
    balance: Float @lambda

type Transaction implements IMetadata {
    objectiveID: ID!
    from: ITransactor
    to: ITransactor!
    amount: Float! @search

I would like to have a lambda that calculates the balance by summing the incoming and outgoing transactions, something like this:

const balance = ({parent: {incomingTransactions, outgoingTransactions}}) => {
  const totalIncoming = incomingTransactions.reduce(((pv, cv) => { pv += cv.amount; return pv; }), 0.0);
  const totalOutgoing = outgoingTransactions.reduce(((pv, cv) => { pv += cv.amount; return pv; }), 0.0);
  return totalIncoming - totalOutgoing;

    "ITransactor.balance": balance

However, it looks like I can’t access the incomingTransactions and outgoingTransaction fields in the lambda query from the parent object. Is this by design? Is it because they are array fields? If so, is there a way to accomplish what I need?

Also just some feedback - it’s pretty difficult to debug lambdas as they are setup :man_shrugging: - e.g. the logs are unresponsive and not very informative, there’s no typing, etc.