sys.stdout.buffer has incorrect type?

mypy test.py
test.py:10: error: Argument 1 to "test" has incompatible type "BinaryIO"; expected "BufferedIOBase"

cat test.py

import io
import sys

class C(io.BufferedIOBase):
  pass

def test(c: io.BufferedIOBase):
  assert isinstance(c, io.BufferedIOBase)

test(sys.stdout.buffer)
test(C())

python3 test.py

As we can see the isinstance check passes but mypy asserts

首先对 test.py 中的复现代码运行 mypy 命令，并检查 Python 标准库中针对 sys.stdout.buffer 入口点的存根。将其声明类型与运行时的 isinstance 结果进行比较，然后通过对示例重新运行 mypy 来验证修正后的行为。