Update method no updating the block

I am unable to update the Block via the `update` method.

method
```
update(id?: string, data?: BlockToolData): void
```

Example: I tried:
```
const blockToUpdate = {
type: 'paragraph',
data: {
text: 'Update Block'
}
};

const blockIndex = editor.blocks.getCurrentBlockIndex();
editor.blocks.update(blockIndex.toString(), blockToUpdate.data);
```

is `blockIndex` the right id I am passing to the update method?