public Builder addBinaryAnnotation(String key, String value, Endpoint endpoint) {
      if (value == null) throw new NullPointerException("value == null");
      if (EMPTY_ENDPOINT.equals(endpoint)) endpoint = null;
      if (binaryAnnotations == null) binaryAnnotations = new ArrayList<>(4);
      binaryAnnotations.add(new V1BinaryAnnotation(key, value, endpoint));
      return this;
    }
Creates a tag annotation, which is the same as {@link Span#tags()} except duplicating the
endpoint.

<p>A key of "lc" and empty value substitutes for {@link Span#localEndpoint()}.
zipkin/src/main/java/zipkin2/v1/V1Span.java