Azure DevOps OData Query Expand Column error

Area, Iteration and AssignedTo are expandable fields, so need to be added to the expand section of the query, not the select section. See also: https://learn.microsoft.com/en-us/azure/devops/report/powerbi/sample-boards-openbugs?view=azure-devops&tabs=powerbi as an example

let
Source = OData.Feed ("https://analytics.dev.azure.com/{organization}/{project}/_odata/v3.0-preview/WorkItems?"
&"$filter=WorkItemType eq 'Bug' "
&"and StateCategory ne 'Completed' "
&"and startswith(Area/AreaPath,'{areapath}') "
&"&$select=WorkItemId,Title,WorkItemType,State,Priority,Severity,TagNames,AreaSK "
&"&$expand=AssignedTo($select=UserName),Iteration($select=IterationPath),Area($select=AreaPath) "
,null, [Implementation="2.0",OmitValues = ODataOmitValues.Nulls,ODataVersion = 4]) 
in
Source

Area, Iteration and AssignedTo are expandable fields, so need to be added to the expand section of the query, not select. See also: https://learn.microsoft.com/en-us/azure/devops/report/powerbi/sample-boards-openbugs?view=azure-devops&tabs=powerbi as an example