Problem: BytesIO class does not have a flush() method. CPython implements it by checking if closed and returning None.

RustPython Location: crates/vm/src/stdlib/io.rs:4530-4750 - no flush() pymethod found

CPython 3.14 Reference: Modules/_io/bytesio.c:325-335

static PyObject *
_io_BytesIO_flush_impl(bytesio *self)
/*[clinic end generated code: output=d39776f1c4ccf3b2 input=7a5cfc61b68aadc1]*/
{
    CHECK_CLOSED(self);
    Py_RETURN_NONE;
}