Smile\ElasticsuiteCatalog\Model\ResourceModel\Product\Advanced\Collection::addFieldsToFilter PHP Method

    public function addFieldsToFilter($fields)
    {
        if ($fields) {
            foreach ($fields as $fieldByType) {
                foreach ($fieldByType as $attributeId => $condition) {
                    $attributeCode = $this->getEntity()->getAttribute($attributeId)->getAttributeCode();
                    $condition = array_filter($condition, 'strlen');
                    $this->addFieldToFilter($attributeCode, $condition);
                }
            }
        }
        return $this;
    }