* @cell: The #GtkCellRenderer that is being rendered by @tree_column
* @tree_model: The #GtkTreeModel being rendered
* @iter: A #GtkTreeIter of the current row rendered
* @cell: The #GtkCellRenderer that is being rendered by @tree_column
* @tree_model: The #GtkTreeModel being rendered
* @iter: A #GtkTreeIter of the current row rendered