Method delete

/**
 * Method to delete a user, user groups, and any other necessary data from the database.
 *
 * @param   integer  $userId  An optional user id.
 *
 * @return  boolean  True on success, false on failure.
 *
 * @since   1.7.0
 */
public function delete($userId = null)
{
    // Set the primary key to delete.
    $k = $this->_tbl_key;
    if ($userId) {
        $this->{$k} = (int) $userId;
    }
    $key = (int) $this->{$k};
    // Delete the user.
    $query = $this->_db->getQuery(true)->delete($this->_db->quoteName($this->_tbl))->where($this->_db->quoteName($this->_tbl_key) . ' = :key')->bind(':key', $key, ParameterType::INTEGER);
    $this->_db->setQuery($query);
    $this->_db->execute();
    // Delete the user group maps.
    $query->clear()->delete($this->_db->quoteName('#__user_usergroup_map'))->where($this->_db->quoteName('user_id') . ' = :key')->bind(':key', $key, ParameterType::INTEGER);
    $this->_db->setQuery($query);
    $this->_db->execute();
    /*
     * Clean Up Related Data.
     */
    $query->clear()->delete($this->_db->quoteName('#__messages_cfg'))->where($this->_db->quoteName('user_id') . ' = :key')->bind(':key', $key, ParameterType::INTEGER);
    $this->_db->setQuery($query);
    $this->_db->execute();
    $query->clear()->delete($this->_db->quoteName('#__messages'))->where($this->_db->quoteName('user_id_to') . ' = :key')->bind(':key', $key, ParameterType::INTEGER);
    $this->_db->setQuery($query);
    $this->_db->execute();
    $query->clear()->delete($this->_db->quoteName('#__user_keys'))->where($this->_db->quoteName('user_id') . ' = :username')->bind(':username', $this->username);
    $this->_db->setQuery($query);
    $this->_db->execute();
    return true;
}