How to use GroupOfStopPlaces ?

example-groupofentities.xml

<?xml version="1.0" encoding="utf-8"?>
<PublicationDelivery xmlns="http://www.netex.org.uk/netex" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:gml="http://www.opengis.net/gml/3.2" xmlns:siri="http://www.siri.org.uk/siri" version="1.04:NO-NeTEx-networktimetable:1.0">
<PublicationTimestamp>2018-12-18T12:00:00.0Z</PublicationTimestamp>
  <ParticipantRef>enRoute</ParticipantRef>
  <dataObjects>
    <CompositeFrame version="any" id="chouette:CompositeFrame:1">
      <frames>
        <SiteFrame version="any" id="chouette:SiteFrame:1">
          <stopPlaces>
            <!-- little child -->
            <StopPlace version="any" created="2017-05-17T17:08:37.0Z" changed="2017-10-11T09:22:36.0Z" id="chouette:StopArea:3ffe3320-071e-4d5c-b58e-ef8dbd163a27:LOC">
              <Name>Westborough North Station</Name>
              <placeTypes>
                <TypeOfPlaceRef ref="generalStopPlace"/>
              </placeTypes>
            </StopPlace>
          </stopPlaces>
        </SiteFrame>

        <GeneralFrame version="any" id="chouette:OtherStopPlaces:1">
          <Name>SiteFrame extension</Name>
          <Description>Extensions to SiteFrame content</Description>
          <members>
            <!-- GeneralGroupOfEntities GroupOfStopPlaces example -->
            <GeneralGroupOfEntities version="any" created="2018-04-21T10:04:37.0Z" changed="2018-04-21T10:04:37.0Z" id="chouette:StopArea:1ebb52c6-b96e-411a-9df7-bd6c90bc6fa9:LOC">
              <Name>Willowbrook Station</Name>
              <PurposeOfGroupingRef ref="chouette:PurposeOfGrouping:groupOfStopPlace"/>
              <PrivateCode>BXF</PrivateCode>

              <members>
               <StopPlaceRef ref="chouette:StopArea:3ffe3320-071e-4d5c-b58e-ef8dbd163a27:LOC"/>
              </members>
            </GeneralGroupOfEntities>

            <ValueSet version="any" id="chouette:ValueSet:1">
              <values>
                <PurposeOfGrouping version="any" id="chouette:PurposeOfGrouping:groupOfStopPlace">
                  <Name>Group of Stop Place</Name>
                  <classes>
                    <ClassRef nameOfClass="StopPlace"/>
                  </classes>
                </PurposeOfGrouping>
              </values>
            </ValueSet>
          </members>
        </GeneralFrame>
      </frames>
    </CompositeFrame>
  </dataObjects>
</PublicationDelivery>

example-groupofstopplaces.xml

<?xml version="1.0" encoding="utf-8"?>
<PublicationDelivery xmlns="http://www.netex.org.uk/netex" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:gml="http://www.opengis.net/gml/3.2" xmlns:siri="http://www.siri.org.uk/siri" version="1.04:NO-NeTEx-networktimetable:1.0">
<PublicationTimestamp>2018-12-18T12:00:00.0Z</PublicationTimestamp>
  <ParticipantRef>enRoute</ParticipantRef>
  <dataObjects>
    <CompositeFrame version="any" id="chouette:CompositeFrame:1">
      <frames>
        <SiteFrame version="any" id="chouette:SiteFrame:1">
          <stopPlaces>
            <!-- little child -->
            <StopPlace version="any" created="2017-05-17T17:08:37.0Z" changed="2017-10-11T09:22:36.0Z" id="chouette:StopArea:3ffe3320-071e-4d5c-b58e-ef8dbd163a27:LOC">
              <Name>Westborough North Station</Name>
              <placeTypes>
                <TypeOfPlaceRef ref="generalStopPlace"/>
              </placeTypes>
            </StopPlace>

            <GroupOfStopPlaces version="any" created="2017-05-17T17:08:37.0Z" changed="2017-10-11T09:22:36.0Z" id="chouette:StopArea:1ebb52c6-b96e-411a-9df7-bd6c90bc6fa9:LOC">
              <Name>Westborough Station</Name>
              <members>
               <StopPlaceRef ref="chouette:StopArea:3ffe3320-071e-4d5c-b58e-ef8dbd163a27:LOC"/>
              </members>
            </GroupOfStopPlaces>
          </stopPlaces>
        </SiteFrame>
      </frames>
    </CompositeFrame>
  </dataObjects>
</PublicationDelivery>