this is a multi-request process:
first do a request for places, like desribed here:
Then you can ask a place for its roles, like described here:
The URL to call for the place's roles is already in the response of the places request, you do not need to create the URL manually, but to identify it.
From there you have all information you need, the link to the admin role's members to call is in the response of the place's roles request. Or you can create it manyually with the placeid and roleid you have identified with the calls earlier - if that suits your scenario better.
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