def METHOD_NAME(query_params):
    """Ensure `query_params` includes `content_type` and `field_name` and `content_type` is a valid ContentType.
    Return the 'ContentTypes' model and 'field_name' if validation was successful.
    """
    if "content_type" not in query_params or "field_name" not in query_params:
        raise ValidationError("content_type and field_name are required parameters", code=400)
    contenttype = query_params.get("content_type")
    app_label, model_name = contenttype.split(".")
    try:
        model_contenttype = ContentType.objects.get(app_label=app_label, model=model_name)
        model = model_contenttype.model_class()
        if model is None:
            raise ValidationError(f"model for content_type: <{model_contenttype}> not found", code=500)
    except ContentType.DoesNotExist:
        raise ValidationError("content_type not found", code=404)
    field_name = query_params.get("field_name")
    return field_name, model