public final HttpClientBuilder addRequestInterceptorFirst(final HttpRequestInterceptor interceptor) {
        Args.notNull(interceptor, "Interceptor");
        if (requestInterceptors == null) {
            requestInterceptors = new LinkedList<>();
        }
        requestInterceptors.add(new RequestInterceptorEntry(RequestInterceptorEntry.Position.FIRST, interceptor));
        return this;
    }
Adds this protocol interceptor to the head of the protocol processing list.

@return this instance.
httpclient5/src/main/java/org/apache/hc/client5/http/impl/classic/HttpClientBuilder.java