代码在同一线程上执行但进程不同

Question

有人可以解释为什么此代码在同一线程但在不同进程上执行吗？那怎么可能？

from concurrent.futures import ProcessPoolExecutor
import os
import threading


def whereami():
    print("You are on thread {} and on process {}".format(
        threading.get_ident(), os.getpid()))


with ProcessPoolExecutor() as pool:
    whereami()
    pool.submit(whereami)