get: 
  tags:
    - Population statistics
  operationId: groupByItems
  summary: Group-by items
  parameters: 
    - $ref: '../zoo-api.yaml#/components/parameters/AgbSubject'
      required: true
  responses:
    200:
      description: |-
        Returns a list of all available group-by items for the _common statistics_ end point, but only if the items are available for the customer with `agb`. The output of this end point should be the same as the documentation below.
      content: 
        application/json:
          schema:
            type: array
            items: 
              $ref: ../schemas/StatisticsGroupBy-enum.yaml
    400:
      $ref: '../zoo-api.yaml#/components/responses/ReqFailure'
    401:
      $ref: '../zoo-api.yaml#/components/responses/JwtFailure'
    404:
      $ref: '../zoo-api.yaml#/components/responses/PatNotFound'