import asyncio
from typing import Any, List, Optional

def chunker( limit: int ) -> Any:

    async def process( q_in: asyncio.Queue[ Any ],
                       q_out: asyncio.Queue[ Any ] ) -> None:

        s = ''
        while True:
            item = await q_in.get()
            print( "{}, retrieved {}".format( limit, item ) )

            if item is None:
                while s:
                    if len( s ) <= limit:
                        await q_out.put( str( s ) )
                        s = ''
                    else:
                        await q_out.put( str( s[:limit] ) )
                        s = s[ limit : ]
                break

            s += item
            if len( s ) < limit:
                continue
            if len( s ) <= limit:
                await q_out.put( str( s ) )
                s = ''
                continue
            else:
                await q_out.put( str( s[ :limit ] ) )
                s = s[ limit : ]
                continue

            await q_out.put( s )

        await q_out.put( None )

    return process

import run_tests