Issues with using stack.fork

[muelleel]

Hi, we have an Problem with the fork function of the stack.

We used the code from your example

# LEGO type:advanced slot:0 autostart

import runtime
import sys
import system

async def main(vm, stack):
    done = False 
    async def fork(): 
        print("Test") # replace with your code to be run in parallel 
        nonlocal done 
        done = True 
    stack.fork("fork", fork()) 
    print("test2")
    while not done: 
        yield 
    # at this point both operations will be complete 
    vm.stop()

def setup(rpc, system, stop):
    vm = runtime.VirtualMachine(rpc, system, stop, "hello_world")
    vm.register_on_start("main_on_start", main)
    return vm

The code exits immediatilly extits with following message:

Traceback (most recent call last):
  File "event_loop/event_loop.py", line 1, in step
  File "runtime/stack.py", line 1, in coro
  File "./projects/996/__init__.py", line 13, in main
AttributeError: 'Stack' object has no attribute 'fork'

Can you help with this? How can we execute multiple things simultaneously?
Thank you