import builtins
import asyncio

async def agen():
    for i in range(3):
        yield i

async def main():
    aiter = agen()
    val1 = await builtins.anext(aiter)
    print("val1:", val1)
    val2 = await builtins.anext(aiter)
    print("val2:", val2)

    val3 = await builtins.anext(aiter, "done")
    print("val3:", val3)

asyncio.run(main())

import asyncio

async def simple_test():
    async def agen():
        yield 1
    
    aiter = agen()
    print(f"First value: {await anext(aiter)}")
    
    # EXPECTED: Should return "no more values"
    result = await anext(aiter, "no more values")
    print(f"Second value: {result}")

if __name__ == "__main__":
    asyncio.run(simple_test())

#Cpython 
First value: 1
Second value: no more values

#RustPython

    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.15s
     Running `target/debug/rustpython /home/yash/test_anext_simple.py`
First value: 1
Traceback (most recent call last):
  File "/home/yash/test_anext_simple.py", line 22, in <module>
    asyncio.run(simple_test())
  File "/home/yash/contri/RustPython/pylib/Lib/asyncio/runners.py", line 193, in run
    with Runner(debug=debug, loop_factory=loop_factory) as runner:
  File "/home/yash/contri/RustPython/pylib/Lib/asyncio/runners.py", line 194, in run
    return runner.run(main)
  File "/home/yash/contri/RustPython/pylib/Lib/asyncio/runners.py", line 129, in run
    signal.signal(signal.SIGINT, signal.default_int_handler)
  File "/home/yash/contri/RustPython/pylib/Lib/asyncio/runners.py", line 124, in run
    raise  # CancelledError
  File "/home/yash/contri/RustPython/pylib/Lib/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
  File "/home/yash/contri/RustPython/pylib/Lib/asyncio/base_events.py", line 687, in run_until_complete
    return future.result()
  File "/home/yash/contri/RustPython/pylib/Lib/asyncio/futures.py", line 203, in result
    raise self._exception.with_traceback(self._exception_tb)
  File "/home/yash/contri/RustPython/pylib/Lib/asyncio/tasks.py", line 314, in __step_run_and_handle_result
    result = coro.send(None)
  File "/home/yash/test_anext_simple.py", line 18, in simple_test
    result = await anext(aiter, "no more values")
StopAsyncIteration