pub fn Graph(comptime T: type) type {
    return struct {
        constants: std.ArrayList(T),

        pub fn init(allocator: *std.mem.Allocator) Graph(T) {
            return .{ .constants = std.ArrayList(T).init(allocator) };
        }

        pub fn constant(graph: *Graph(T), value: T) !void {
            try graph.constants.append(value);
        }
    };
}
const GraphT = Graph(i32);
const constant = GraphT.constant;

test "create graph" {
    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
    defer arena.deinit();
    const allocator = &arena.allocator;

    var graph = &GraphT.init(allocator);
    const x = try constant(graph, 5);
    const y = try constant(graph, 10);
}