public function stats_send($template = null, $start_date = null, $end_date = null, array $data = [])
{
$data['stat'] = 'send';
if (!is_null($template)) {
$data['template'] = $template;
}
if (!is_null($start_date)) {
$data['start_date'] = $start_date;
}
if (!is_null($end_date)) {
$data['end_date'] = $end_date;
}
return $this->stats($data);
}