code: def submit_future(self, func, *args, **kwargs):
          
          # This mode will run futures synchronously. This should only be used
          # for benchmarking purposes.
          if self.config["sync_http"] is True:
              return MockFuture(func, *args, **kwargs)
  
          future = self.pool.submit(func, *args, **kwargs)
          self.futures.append(future)
          return future
docs: Submit a function call to be run as a future in a thread pool. This
          should be an I/O bound operation.