public function addFieldValueFactorFunction($field, $factor, $modifier = 'none', BuilderInterface $query = null)
    {
        $function = [
            'field_value_factor' => [
                'field' => $field,
                'factor' => $factor,
                'modifier' => $modifier,
            ],
        ];

        $this->applyFilter($function, $query);

        $this->functions[] = $function;

        return $this;
    }