protected function getValuesJSON() {
		$value = $this->value;
		if($value instanceof SS_List) {
			$values = $value->column($this->idField);
		}
		else if(is_array($value)) {
			$values = array_keys($value);
		}
		else if(is_string($value)) {
			$values = explode(',', $value);
			$values = str_replace('{comma}', ',', $values);
		}

		return $this->formatJSON($this->source->filter(array(
			$this->idField => $values
		)));
	}