Method increment_generation

src/sharedref.rs:270–275

(&self, py: Python)

    }

    fn increment_generation(&self, py: Python) {
        assert_eq!(self.current_borrow_count(py), 0);
        // this wraps around to the same value if mutably borrowed
        // usize::MAX times, which wouldn't happen in practice.
        self.generation.fetch_add(1, Ordering::Relaxed);
    }
}

/// Helper to keep the borrow count updated while the shared object is