TreeViewRowSeparatorFunc    
    Function type for determining whether the row pointed to by @iter should be rendered as a separator. A common way to implement this is to have a boolean column in the model, whose values the GtkTreeViewRowSeparatorFunc returns.
- param - modelthe- GtkTreeModel
- param - itera- GtkTreeIterpointing at a row in @model
- return true if the row is a separator