protected function getFilterField(\Magento\Catalog\Model\ResourceModel\Eav\Attribute $attribute)
    {
        return $this->mappingHelper->getFilterField($attribute);
    }
protected function getFilterField(\Magento\Catalog\Model\ResourceModel\Eav\Attribute $attribute)
    {
        return $this->mappingHelper->getFilterField($attribute);
    }
protected function getFilterField ( \ Magento \ Catalog \ Model \ ResourceModel \ Eav \ Attribute $ attribute ) { return $ this -> mappingHelper -> getFilterField ( $ attribute ) ; }
Retrieve ES filter field.

@param \Magento\Catalog\Model\ResourceModel\Eav\Attribute $attribute The attribute

@return string
Retrieve ES filter field .