code: public static Tag exception(@Nullable Throwable exception) {
          if (exception == null) {
              return EXCEPTION_NONE;
          }
          String simpleName = exception.getClass().getSimpleName();
          return Tag.of("exception", simpleName.isEmpty() ? exception.getClass().getName() : simpleName);
      }
docs: Creates a {@code exception} tag based on the {@link Class#getSimpleName() simple
  name} of the class of the given {@code exception}.
  
  @param exception the exception, may be {@code null}
  @return the exception tag derived from the exception