??? Attempt to reference field of non-structure array.

Error in ==> displacement>real_loops at 137
    loops = [Travel.(a) Travel.(b) Travel.(c)];

Error in ==> displacement>loop at 85
    loops       = real_loops(back_codon, codon, there_codon);

Error in ==> displacement at 38
        loop(seq(index:index+4), k);

Error in ==> draw_sine at 64
    displacement(seq(13:end), signal, [], @helper);