Hello, I am new to Klaviyo and I would like to make a back in stock API call out of my Shopify store, like explained here. I do not understand the error: is my products do not have a variant, only a product ID. And maybe I miss understood the concept of a relationship. I thought I am creating one by assigning a product to a profile by this query. Maybe someone can help me.

# URL
url = "https://a.klaviyo.com/client/back-in-stock-subscriptions/?company_id=myID"

# Body
body = {
  "data": {
    "type": "back-in-stock-subscription",
    "attributes": {
      "profile": {
        "data": {
            "type": "profile",
            "attributes": {
                "email": "email@mail.com"
            }
        }
      },
      "channels": ""EMAIL"]
    },
    "relationships": {
      "product": {
        "data": {
          "type": "catalog-variant",
          "id": "$shopify:::$default:::productID"
        }
      }
    }
  }
}

I get the error code:

Response Text: {"errors":r{"id":"dfae79b0-0dd5-46e4-9b3c-7906e4ed4280","status":404,"code":"variant_not_found","title":"The variant in your relationship payload does not exist","detail":"The variant in your relationship payload does not exist","source":{"pointer":"/data/relationships/variant/data/id"},"links":{},"meta":{}}]}