Magento 2 Override Magento\Paypal\Model\Payflowpro::isAvailable()

I want to override isAvailable() method of Magento\Paypal\Model\Payflowpro.php

I have tried below steps but it is not working for me.

app/code/Moduleoverride/Payflowpaypal/etc/module.xml

<?xml version="1.0"?> <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd"> <module name="Moduleoverride_Payflowpaypal" setup_version="1.0.1"> </module> </config> 

app/code/Moduleoverride/Payflowpaypal/registration.php

<?php \Magento\Framework\Component\ComponentRegistrar::register( \Magento\Framework\Component\ComponentRegistrar::MODULE, 'Moduleoverride_Payflowpaypal', __DIR__ ); 

app/code/Moduleoverride/Payflowpaypal/etc/di.xml

<?xml version="1.0"?> <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd"> <preference for="Magento\Paypal\Model\Payflowpro" type="Moduleoverride\Payflowpaypal\Model\Payflowpro" /> </config> 

app/code/Moduleoverride/Payflowpaypal/Model/Payflowpro.php

namespace Moduleoverride\Payflowpaypal\Model;  class Payflowpro extends \Magento\Paypal\Model\Payflowpro {   public function isAvailable(\Magento\Quote\Api\Data\CartInterface $  quote = null)     { echo "This is working";exit;     } }