public function deleteAttachment($nb_attachment) : bool
    {
        $retval = false;
        $nb_attachment_id = nb_getMixedValue($nb_attachment, NABU_ICONTACT_PROSPECT_ATTACHMENT_FIELD_ID);

        if (is_numeric($nb_attachment_id)) {
            $nb_attachment = $this->nb_attachment_list->getItem($nb_attachment_id);
            if ($nb_attachment->getIContactProspectId() == $this->getId()) {
                $nb_attachment->deleteFile();
                $this->nb_attachment_list->removeItem($nb_attachment);
                $nb_attachment->delete();

                $retval = true;
            }
        }

        return $retval;
    }