Function print_ast_list_generic 

pub fn print_ast_list_generic<T>(
    node: &str,
    collection: impl IntoIterator<Item = T>,
    f: impl Fn(T) -> String,
    s: &dyn Symbols,
) -> String

A function used by TreeBuilder::list and TreeBuilder::list_map for list formatting. Also see print_ast_list_without_node_name.