curl --request GET \
  --url https://api.hubapi.com/crm/v3/objects/partner_clients/{partnerClientId}/associations/{toObjectType} \
  --header 'Authorization: Bearer <token>'

{
  "results": [
    {
      "id": "<string>",
      "type": "deal_to_contact"
    }
  ],
  "paging": {
    "next": {
      "after": "NTI1Cg%3D%3D",
      "link": "?after=NTI1Cg%3D%3D"
    }
  }
}