in flink-connector-gcp-pubsub/src/main/java/org/apache/flink/streaming/connectors/gcp/pubsub/common/PubSubDeserializationSchema.java [75:80]
default void deserialize(PubsubMessage message, Collector<T> out) throws Exception {
T deserialized = deserialize(message);
if (deserialized != null) {
out.collect(deserialized);
}
}