public static <M> SinkOperatorSpec<M> createSinkOperatorSpec(SinkFunction<? super M> sinkFn, String opId) {
    return new SinkOperatorSpec<>((SinkFunction<M>) sinkFn, opId);
  }
Creates a {@link SinkOperatorSpec} for the sink operator.

@param sinkFn  the sink function provided by the user
@param opId  the unique ID of the operator
@param <M>  type of input message
@return  the {@link SinkOperatorSpec} for the sink operator
samza-core/src/main/java/org/apache/samza/operators/spec/OperatorSpecs.java