def list(self, order_id, **params):
_, _, line_items = self.http_client.get("<STR_LIT>".format(order_id=order_id), params=params)<EOL>return line_items<EOL>
Retrieve order's line items

Returns all line items associated to order

:calls: ``get /orders/{order_id}/line_items``
:param int order_id: Unique identifier of a Order.
:param dict params: (optional) Search options.
:return: List of dictionaries that support attriubte-style access, which represent collection of LineItems.
:rtype: list