docs: private MultipartBody duplicateMultipartBody(MultipartBody body) {
          
          // It is possible to access individual parts by the Content-Id values
          // This MultipartBody is expected to contain 3 parts, 
          // "book1", "book2" and "image". 
          
          // These individual parts have their Content-Type set to 
          // application/xml, application/json and application/octet-stream
          
          // MultipartBody will use the Content-Type value of the individual
          // part to read its data in a type safe way by delegating to a matching 
          // JAX-RS MessageBodyReader provider
          
          Book jaxbBook = body.getAttachmentObject("book1", Book.class);
          Book jsonBook = body.getAttachmentObject("book2", Book.class);
          
          // Accessing individual attachment part, its DataHandler will be 
          // used to access the underlying input stream, the type-safe access
          // is also possible
          
          Attachment imageAtt = body.getAttachment("image");
          
          if ("JAXB".equals(jaxbBook.getName()) && 1L == jaxbBook.getId()
              && "JSON".equals(jsonBook.getName()) && 2L == jsonBook.getId()
              && imageAtt != null) {
              return createMultipartBody(jaxbBook, jsonBook, imageAtt.getDataHandler());
          }
          throw new RuntimeException("Received Book attachment is corrupted");
      }