apex/sdkextensions/framework/api/system-current.txt

// Signature format: 2.0
package android.os.ext {

  public class SdkExtensions {
    method public static int getExtensionVersion(int);
  }

}

package android.os.ext.test {

  @Deprecated public class Test {
    method @Deprecated public void testF();
    method @Deprecated public void testG();
  }

}