public function getLeadChanges($nextPageToken, $fields, $args = array(), $returnRaw = false)
    {
        $args['nextPageToken'] = $nextPageToken;
        $args['fields'] = (array) $fields;

        if (count($fields)) {
            $args['fields'] = implode(',', $fields);
        }

        return $this->getResult('getLeadChanges', $args, true, $returnRaw);
    }