code: public static V1BinaryAnnotation createString(String key, String value, Endpoint endpoint) {
      if (value == null) throw new NullPointerException("value == null");
      return new V1BinaryAnnotation(key, value, endpoint);
    }
docs: Creates a tag annotation, which is the same as {@link Span#tags()} except duplicating the
  endpoint.
  
  <p>A special case is when the key is "lc" and value is empty: This substitutes for the {@link
  Span#localEndpoint()}.