Method delete

/**
 * Method to delete a row from the database table by primary key value.
 *
 * @param   mixed  $pk  An optional primary key value to delete.  If not set the instance property value is used.
 *
 * @return  boolean  True on success.
 *
 * @since   1.7.0
 * @throws  \UnexpectedValueException
 */
public function delete($pk = null)
{
    if (\is_null($pk)) {
        $pk = array();
        foreach ($this->_tbl_keys as $key) {
            $pk[$key] = $this->{$key};
        }
    } elseif (!\is_array($pk)) {
        $pk = array($this->_tbl_key => $pk);
    }
    foreach ($this->_tbl_keys as $key) {
        $pk[$key] = \is_null($pk[$key]) ? $this->{$key} : $pk[$key];
        if ($pk[$key] === null) {
            throw new \UnexpectedValueException('Null primary key not allowed.');
        }
        $this->{$key} = $pk[$key];
    }
    // Pre-processing by observers
    $event = AbstractEvent::create('onTableBeforeDelete', ['subject' => $this, 'pk' => $pk]);
    $this->getDispatcher()->dispatch('onTableBeforeDelete', $event);
    // If tracking assets, remove the asset first.
    if ($this->_trackAssets) {
        // Get the asset name
        $name = $this->_getAssetName();
        /** @var Asset $asset */
        $asset = self::getInstance('Asset');
        if ($asset->loadByName($name)) {
            if (!$asset->delete()) {
                $this->setError($asset->getError());
                return false;
            }
        }
    }
    // Delete the row by primary key.
    $query = $this->_db->getQuery(true)->delete($this->_tbl);
    $this->appendPrimaryKeys($query, $pk);
    $this->_db->setQuery($query);
    // Check for a database error.
    $this->_db->execute();
    // Post-processing by observers
    $event = AbstractEvent::create('onTableAfterDelete', ['subject' => $this, 'pk' => $pk]);
    $this->getDispatcher()->dispatch('onTableAfterDelete', $event);
    return true;
}