0 is the default value for the timeout argument for both blpop and brpop. When the timeout is `0`, the return type is non-nullable. Otherwise the return type is optional.
I tested my change with the following code
```python
from typing import Optional, Tuple
import redis
def test_blpop_timeout(r: redis.Redis) -> None:
a: Tuple[bytes, bytes] = r.blpop('')
b: Tuple[bytes, bytes] = r.blpop('',timeout=0)
c: Optional[Tuple[bytes, bytes]] = r.blpop('', timeout=1)
d: Optional[Tuple[bytes, bytes]] = r.blpop('', timeout=1.0)
def test_brpop_timeout(r: redis.Redis) -> None:
a: Tuple[bytes, bytes] = r.brpop('')
b: Tuple[bytes, bytes] = r.brpop('',timeout=0)
c: Optional[Tuple[bytes, bytes]] = r.brpop('', timeout=1)
d: Optional[Tuple[bytes, bytes]] = r.brpop('', timeout=1.0)
```
