plugins/devkit/testData/codeInsight/extensionAttributeWithAccessors.xml

<idea-plugin>
  <id>com.intellij.myPlugin</id>

  <extensionPoints>
    <extensionPoint name="acc" beanClass="ExtBeanWithAccessors"/>
  </extensionPoints>

  <extensions defaultExtensionNs="com.intellij.myPlugin">
    <acc param="123"/>
  </extensions>

</idea-plugin>