[Flow] silly issue on 'You need to use $propertyMappingConfiguration->allowProperties('__identity')'

[mario chiari]

Hi

I am trying to define a silly createAction as below and can't remember
how to do:

createAction(\TYPO3\Blog\Domain\Model\Blog $blog) { 

$post = new \TYPO3\Blog\Domain\Model\Post();
                     $post->setBlog($blog);
                     $post->setTitle('aaa');
 		     $post->setAuthor('aaa');
                     $post->setMail('aaa');
             	 
     		$this->postRepository->add($post); 
                $blog->addpost($post);
                $this->blogRepository->update($blog); 
		$this->addFlashMessage('bla bla'); 
                $this->redirect('index');
}

I get the error msg: 

Exception while property mapping for target type
"Doctrine\Common\Collections\Collection<\TYPO3\Blog\Domain\Model\Post>",
at property path "": It is not allowed to map property "__identity". You
need to use $propertyMappingConfiguration->allowProperties('__identity')
to enable mapping of this property.

Shame on me, but I do not remember how I do that.
Thanks, Cheers
mario 

ps is there a way to call an action as above from the command line?