It's easy to write a protocol like this:

class P(Protocol):
    def write(self, arg: bytes) -> None: ...

But it's almost never what you want. Typically you'd use a protocol like this for a function that takes an argument p of type P. That function probably does p.write(some_buffer) or possibly p.write(arg=some_buffer), but almost certainly not both. So the protocol should either have a positional-only or a keyword-only arg, but a positional-or-keyword arg is probably a mistake.

I think it would be reasonable for flake8-pyi to warn about this.