@Override
    public Map<String, DescriptionInfo> loadDocStrings(Set<ServiceConfig> serviceConfigs) {
        return serviceConfigs.stream()
                             .flatMap(c -> {
                                 final GrpcService grpcService = c.service().as(GrpcService.class);
                                 assert grpcService != null;
                                 return grpcService.services().stream();
                             })
                             .flatMap(s -> docstringExtractor.getAllDocStrings(s.getClass().getClassLoader())
                                                             .entrySet().stream())
                             .collect(toImmutableMap(Map.Entry<String, String>::getKey,
                                                     (Map.Entry<String, String> entry) ->
                                                             DescriptionInfo.of(entry.getValue()),
                                                     (a, b) -> a));
    }
{@link DocServicePlugin} implementation that supports {@link GrpcService}s.
grpc/src/main/java/com/linecorp/armeria/internal/server/grpc/GrpcDocServicePlugin.java