code: @Nonnull
      private ZipkinAnnotationsStore addBinaryAnnotation(@Nonnull String key, @Nonnull ByteBuffer byteBuffer,
                                                         @Nonnull AnnotationType annotationType, @Nullable Endpoint endpoint) {
          BinaryAnnotation binaryAnnotation = new BinaryAnnotation(key, byteBuffer, annotationType);
          if (endpoint != null) {
              // endpoint is optional - current version of zipkin web doesn't show spans without host though
              binaryAnnotation.setHost(endpoint);
          }
          underlyingSpan.addToBinary_annotations(binaryAnnotation);
          return this;
      }
docs: PRIVATE METHODS