如何自定义Retrofit允许传递null作为path参数的值？

import okhttp3.RequestBody;
import okhttp3.ResponseBody;
import retrofit2.Converter;
import retrofit2.Retrofit;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

public class NullConverterFactory extends Converter.Factory {
    @Override
    public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations, Retrofit retrofit) {
        return new Converter<ResponseBody, Object>() {
            @Override
            public Object convert(ResponseBody value) throws IOException {
                return null;
            }
        };
    }

    @Override
    public Converter<?, RequestBody> requestBodyConverter(Type type, Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {
        return new Converter<Object, RequestBody>() {
            @Override
            public RequestBody convert(Object value) throws IOException {
                return null;
            }
        };
    }
}

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://api.example.com/")
        .addConverterFactory(new NullConverterFactory()) // 使用自定义转换器
        .build();