public function __isset($property)
	{
		if (array_key_exists($property, static::properties()))
		{
			return true;
		}
		elseif (static::relations($property))
		{
			return true;
		}
		elseif ($this->_get_eav($property, true))
		{
			return true;
		}
		elseif (array_key_exists($property, $this->_custom_data))
		{
			return true;
		}

		return false;
	}