Gene Combination Relationship
GET /api/genecombinations/320/relationships/combination_set?format=api
{
    "data": [
        {
            "type": "Combination",
            "id": "OLI466"
        },
        {
            "type": "Combination",
            "id": "OLI993"
        },
        {
            "type": "Combination",
            "id": "OLI994"
        }
    ]
}