44. Bus Error Checker

How do you plan to solve it?

module error_checker_xz(bus,all_known,has_unknown,bus_if_known);
input [7:0]bus;
output all_known,has_unknown;
output [7:0]bus_if_known;
wire any_xz=(^(bus^bus))===1'bx;
assign all_known=~any_xz;
assign has_unknown=any_xz;
assign bus_if_known={all_known}?bus:0;
endmodule