### transact · function

Executes a function within a database transaction context.

Loading models (also through links in other models) and changing models can only be done from
within a transaction.

Transactions have a consistent view of the database, and changes made within a transaction are
isolated from other transactions until they are committed. In case a commit clashes with changes
made by another transaction, the transaction function will automatically be re-executed up to 6
times.

**Signature:** `<T>(fn: () => T) => Promise<T>`

**Type Parameters:**

- `T` - The return type of the transaction function.

**Parameters:**

- `fn: () => T` - The function to execute within the transaction context. Receives a Transaction instance.

**Returns:** A promise that resolves with the function's return value.

**Throws:**

- With code "RACING_TRANSACTION" if the transaction fails after retries due to conflicts.
- With code "TXN_LIMIT" if maximum number of transactions is reached.
- With code "LMDB-{code}" for LMDB-specific errors.

**Examples:**

```typescript
const paid = await E.transact(() => {
  const user = User.get("john_doe");
  if (user.credits > 0) {
    user.credits--;
    return true;
  }
  return false;
});
```
```typescript
// Transaction with automatic retry on conflicts
await E.transact(() => {
  const counter = Counter.get("global") || new Counter({id: "global", value: 0});
  counter.value++;
});
```