code: public function lookupItem($item_id)
  	{
  		$request = new ItemRequest($item_id);
  		$this->emit('request.item', array($item_id));
  		$response = $this->post($request);
  		return new ItemResponse($response);
  	}
docs: Lookup item information from item id
  
  @param  string  $item_id
  @return ItemResponse