How to use the extension point other plugin?

In a plugin has testng extension point:

    <extensionPoints >
      <extensionPoint qualifiedName="com.theoryinpractice.testng.listener" interface="org.testng.IDEATestNGListener"/>
    </extensionPoints>

I want to use this extension point as follows:

     <extensions defaultExtensionNs="TestNG-J">
        <com.theoryinpractice.testng.listener implementation="org.example.MyTestNGListener" />
    </extensions>

But it did not work. What am I doing wrong?

(If there are errors, I'm sorry, did the translation from Google Translate)