`is_connected` does not return a boolean value

[yvan-the-barbarian]

Version: 4.3.4

Description

The is_connected property of the Connection class in redis.asyncio.connection.py returns either None, a StreamReader or a StreamWriter rather than a boolean value as would be expected.

While this will work for all cases where the "truthiness" is checked directly, it could cause weird issues in other cases.

Such as logging the connection state, for example:

# Prints: "Connection connected: <StreamWriter transport=<_ProactorSocketTransport fd=484 read=<_OverlappedFuture pending overlapped=<pending, 0x1666c1aa940> cb=[_ProactorReadPipeTransport._loop_reading()]>> reader=<StreamReader transport=<_ProactorSocketTransport fd=484 read=<_OverlappedFuture pending overlapped=<pending, 0x1666c1aa940> cb=[_ProactorReadPipeTransport._loop_reading()]>>>>"
print(f'Connection connected: {connection.is_connected}')