How can I use async generator expressions

I am trying to replicate the following from PEP 530

generator expression: (i ** 2 async for i in agen()).

with the following code:

import asyncio
async def agen():
    for x in range(5):
         yield x
async def main():
    x = tuple(i ** 2 async for i in agen())

but I get TypeError: 'async_generator' object is not iterable. If I do x = [i ** 2 async for i in agen()] works well.

I understand that the faulty statement is equivalent of tuple(agen()). Then, how / when am I expected to use async generator expressions? Could I get an example?

Thank you!

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Marco Ippolito