public function set($key, $value)
	{
		if ($this->readOnly)
		{
			throw new \RuntimeException('Changing values on this Data Container is not allowed.');
		}

		$this->isModified = true;

		if ($key === null)
		{
			$this->data[] = $value;

			return $this;
		}

		Arr::set($this->data, $key, $value);

		return $this;
	}