subprocess stdout read1

import subprocess
process = subprocess.Popen("echo hello", shell=True, stdout=subprocess.PIPE)
assert process.stdout is not None
print(process.stdout.read1())

mypy error:

asd.py:4: error: "IO[bytes]" has no attribute "read1"; maybe "read"?
Found 1 error in 1 file (checked 1 source file)

But at runtime there is read1() method. It is useful because unlike read(), it will return the output as soon as it is available, instead of reading more until it gets n bytes or end of file.

定位 subprocess.Popen 的 stdout stub，并检查其 stream 类型是如何声明的。使用提供的 Python 代码片段复现该问题，然后验证 mypy 能够接受对 process.stdout 调用 read1()，同时不丢失现有的 stdout 类型标注。