如何在系统verilog中返回关联数组

typedef int unsigned Addr_t;
typedef int unsigned Data_t;

function automatic Addr_t[string] create_associative_array();
    Addr_t[string] associative_array;
    associative_array["key1"] = 1;
    associative_array["key2"] = 2;
    associative_array["key3"] = 3;
    return associative_array;
endfunction

module test;
    Addr_t[string] my_array;

    initial begin
        my_array = create_associative_array();
        $display("Value of key1: %0d", my_array["key1"]);
        $display("Value of key2: %0d", my_array["key2"]);
        $display("Value of key3: %0d", my_array["key3"]);
    end
endmodule