Sink log entries to storage.

def sink_storage(client, to_delete):
    """Sink log entries to storage."""
    bucket = _sink_storage_setup(client)
    to_delete.append(bucket)
    SINK_NAME = "robots-storage-%d" % (_millis(),)
    FILTER = "textPayload:robot"

    # [START sink_storage_create]
    DESTINATION = "storage.googleapis.com/%s" % (bucket.name,)
    sink = client.sink(SINK_NAME, filter_=FILTER, destination=DESTINATION)
    assert not sink.exists()  # API call
    sink.create()  # API call
    assert sink.exists()  # API call
    # [END sink_storage_create]
    to_delete.insert(0, sink)