Script property using function don't work with blocks

In Components & JS docs there's this example:

editor.BlockManager.add('test-block', {
  label: 'Test block',
  attributes: {class: 'fa fa-text'},
  content: {
    script: "alert('Hi'); console.log('the element', this)",
    // Add some style just to make the component visible
    style: {
      width: '100px',
      height: '100px',
      'background-color': 'red',
    }
  }
});

This works perfectly. But I couldn't use a function instead of a string in script, as is said it's supported like this example:

editor.BlockManager.add('test-block', {
  ...
  content: {
    script: function () {
      alert('Hi');
      console.log('the element', this);
    },
    ...
  }
});

It won't happen anything. The documentation isn't very clear about using scripts in blocks or components.