Variant Relationship
GET /api/variants/2157/relationships/gene_name?format=api
{
    "data": {
        "type": "Gene",
        "id": "TG"
    }
}
              GET /api/variants/2157/relationships/gene_name?format=api
{
    "data": {
        "type": "Gene",
        "id": "TG"
    }
}