Updating an Insertion Order in Bing Ads API using Python

Question

Hello

I am trying to update an existing Insertion Order in an account through the usage of the API. I can do this through the Web UI but I need to replicate it using code. My aim with the existing Insertion Order is to set the SpendCapAmount to Unlimited and to set the End Dateto empty so that there is no end date.

My SOAP request made through the Bing API is as follows:

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tns="https://bingads.microsoft.com/Billing/v13" xmlns:ns0="https://bingads.microsoft.com/Customer/v13/Entities" xmlns:ns1="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns2="https://bingads.microsoft.com/Billing/v13">
   <SOAP-ENV:Header>
      <tns:AuthenticationToken>XXX</tns:AuthenticationToken>
      <tns:DeveloperToken>XXX</tns:DeveloperToken>
   </SOAP-ENV:Header>
   <ns1:Body>
      <ns2:UpdateInsertionOrderRequest>
         <ns2:InsertionOrder>
            <ns0:AccountId>123456</ns0:AccountId>
            <ns0:Id>67890</ns0:Id>
            <ns0:Status>Active</ns0:Status>
            <ns0:PendingChanges>
               <ns0:EndDate>Nil</ns0:EndDate>
               <ns0:SpendCapAmount>Nil</ns0:SpendCapAmount>
               <ns0:ChangeStatus>ApproveChanges</ns0:ChangeStatus>
            </ns0:PendingChanges>
         </ns2:InsertionOrder>
      </ns2:UpdateInsertionOrderRequest>
   </ns1:Body>
</SOAP-ENV:Envelope>

This request gets made but I get hit with a WebFault error: "The string 'Nil' is not a valid AllXsd value."

Assuming that what I want above is possible, whats the correct values to set to those two attributes?