public static <M, WK, WV> WindowOperatorSpec<M, WK, WV> createWindowOperatorSpec(
      WindowInternal<M, WK, WV> window, String opId) {
    return new WindowOperatorSpec<>(window, opId);
  }
Creates a {@link WindowOperatorSpec}.

@param window  the description of the window.
@param opId  the unique ID of the operator
@param <M>  the type of input message
@param <WK>  the type of key in the window output
@param <WV>  the type of value in the window
@return  the {@link WindowOperatorSpec}
samza-core/src/main/java/org/apache/samza/operators/spec/OperatorSpecs.java