How to summarize by Severity Level in Azure Application Insights Logs for each operation name

I have multiple azure functions in single azure function app resource where each function logs are stored with function name inoperation_Name column of application insights logs. For all azure functions names, I am logging messages with Warnings(severityLevel=2) and Errors(severityLevel=3).

Expected: I am trying to show all functions warnings, errors in a single pie chart and later to pin to dashboard. Piechart should give us visibility how many errors and warnings for each function have in a single azure function app resource.

Actual: Pie chart is displaying for all severity levels(combining) for each function name(operationname) for a single azure function app resource.

traces
| where severityLevel >1
| where cloud_RoleName == 'dev-test-functionapp' //Azure Function App Resource Name
| where operation_Name in ('Function1Name','Function2Name','Function3Name')
| summarize by operation_Name,severityLevel
| render piechart 

>Solution :

If I understand correctly, this could work:

traces
| where severityLevel > 1
| extend severityLevel = case(severityLevel == 2, "Warning", severityLevel == 3, "Error", tostring(severityLevel))
| where cloud_RoleName == 'dev-test-functionapp'
| where operation_Name in ('Function1Name','Function2Name','Function3Name')
| summarize count() by s = strcat(severityLevel, "_", operation_Name)
| render piechart