Awaits in async block fora next message sent to the inbox. Returns None if message is incompatible with expected response type.

Receives a next message sent to the inbox, which satisfies provided predicate. This is a blocking operation. Returns None if timeout occurred or message is incompatible with expected response type.

Creates an actor-like object, which could be interrogated from the outside. Usually it's used to spy on other actors lifecycle. Most of the inbox methods works in thread-blocking manner.

Receives a next message sent to the inbox. This is a blocking operation. Returns None if timeout occurred or message is incompatible with expected response type.