connecting ports by name

This problem is similar to module. You are given a module named mod_a that has 2 outputs and 4 inputs, in some order. You must connect the 6 ports by name to your top-level module's ports:

代码如下：

module top_module ( 
    input a, 
    input b, 
    input c,
    input d,
    output out1,
    output out2
);
    mod_a instance1(.out1(out1),.out2(out2),.in1(a),.in2(b),.in3(c),.in4(d));
endmodule