code: public static HttpResponse fromStream(HttpHeaders headers,
                                            Stream<? extends ServerSentEvent> contentStream,
                                            HttpHeaders trailingHeaders, Executor executor) {
          requireNonNull(headers, "headers");
          requireNonNull(contentStream, "contentStream");
          requireNonNull(trailingHeaders, "trailingHeaders");
          requireNonNull(executor, "executor");
          return streamingFrom(contentStream, sanitizeHeaders(headers), trailingHeaders,
                               ServerSentEvents::toHttpData, executor);
      }
docs: Creates a new Server-Sent Events stream from the specified {@link Stream}.
  
  @param headers the HTTP headers supposed to send
  @param contentStream the {@link Stream} which publishes the objects supposed to send as contents
  @param trailingHeaders the trailing HTTP headers supposed to send
  @param executor the executor which iterates the stream