docs: async def main():
      """`sublemon` library example!"""
      for c in (1, 2, 4,):
          async with Sublemon(max_concurrency=c) as s:
              start = time.perf_counter()
              await asyncio.gather(one(s), two(s))
              end = time.perf_counter()
              print('Limiting to', c, 'concurrent subprocess(es) took',
                    end-start, 'seconds\n')