I want to implement plugin after,before and around concept in my magento2 website.

di.xml

<type name="Magento\Webapi\Model\Soap\Server">
        <plugin name="soap_log" type="training\learning\Model\Webapi\Soap\Server" />
 </type>

Magento\Webapi\Model\Soap\Server has a method _checkRequest and it has a string type parameter.

Now i want to get that string type parameter in my _aftercheckrRequest in training\learning\Model\Webapi\Soap\Server class. How can I achieve this ?