I am overriding `Magento\Catalog\Block\Product\ListProduct`
In function `_getProductCollection` I have added some extra code. 

```
public function _getProductCollection()
{ 
 $collection = parent::_getProductCollection(); 
 $collection->addAttributeToFilter('attribute', array('operator' =>
        'value')) 
    return $collection  
}

```

But my collection in not attaching this attribute. I am getting only default collection except adding `operator` attribute

Any idea ??