public function getFilterSubmitButton()
	{
		if ($this->hasAutoSubmit()) {
			throw new DataGridException(
				'DataGrid has auto-submit. Turn it off before setting filter submit button.'
			);
		}

		if ($this->filter_submit_button === null) {
			$this->filter_submit_button = new Filter\SubmitButton($this);
		}

		return $this->filter_submit_button;
	}