@Override
    public Builder requestInterceptor(final RequestInterceptor requestInterceptor) {
      checkNotNull(requestInterceptor, "Argument requestInterceptor must be not null");
      this.requestInterceptors.add(requestInterceptor);
      return this;
    }
Adds a single request interceptor to the builder.

@param requestInterceptor request interceptor to add
@return this builder
vertx/feign-vertx/src/main/java/feign/VertxFeign.java