def METHOD_NAME(self, validated_data):
    # Creating a new node, by default put it in the clipboard root.
    if "parent" not in validated_data:
        if "request" in self.context and self.context["request"].user:
            validated_data["parent_id"] = self.context[
                "request"
            ].user.clipboard_tree_id
        else:
            raise ValidationError(
                "Trying to create a clipboard node when there is no user"
            )
    try:
        channel_query = Channel.objects.filter(
            main_tree__tree_id=OuterRef("tree_id")
        )
        ContentNode.objects.all().annotate(
            # Annotate channel id
            channel_id=Subquery(channel_query.values_list("id", flat=True)[:1])
        ).get(
            node_id=validated_data["source_node_id"],
            channel_id=validated_data["source_channel_id"],
        )
    except ContentNode.DoesNotExist:
        raise ValidationError("ContentNode does not exist")
    return super(ClipboardSerializer, self).METHOD_NAME(validated_data)