What is the name of the shipping agent of the document with id 2?
SELECT Ref_Shipping_Agents.shipping_agent_name FROM Ref_Shipping_Agents JOIN Documents ON Documents.shipping_agent_code = Ref_Shipping_Agents.shipping_agent_code WHERE Documents.document_id = 2;
SELECT Ref_Shipping_Agents.shipping_agent_name FROM Ref_Shipping_Agents JOIN Documents ON Documents.shipping_agent_code = Ref_Shipping_Agents.shipping_agent_code WHERE Documents.document_id = 2;
[{'shipping_agent_name': 'USPS'}]