public RouteBuilder produces(MediaType... produceTypes) {
        produces(ImmutableSet.copyOf(requireNonNull(produceTypes, "produceTypes")));
        return this;
    }
Sets the {@link Route} to produce the specified {@link MediaType}s. If not set,
the mapped {@link HttpService} accepts {@link HttpRequest}s that have any
{@link HttpHeaderNames#ACCEPT}. In order to get this work, {@link #methods(Iterable)} must be set.
core/src/main/java/com/linecorp/armeria/server/RouteBuilder.java