dbapi2.Cursor.description property type annotation should be Optional[...]

[jsurany]

The dbapi2.Cursor._description can be null, so the accessor should be an Optional type.

>>> from comdb2 import dbapi2
>>> conn = dbapi2.connect("....")
>>> cursor = conn.cursor()
>>> type(cursor.description)
<class 'NoneType'>

The type annotation for the property is tuple[tuple[str, object, None, None, None, None, None], ...]