You are given a code:

def main_solution(x):
    return (func_13(x, '_') + (x + 'ytlmtu'))

Can you predict the output of `main_solution("taybnnlom")` without writing any code? Please reason and put your final answer in the following json format: {"output": <your output>}, where <your output> should be the final string.
user
{"ref_input": {"x": "taybnnlom"}, "ref_output": "t_a_y_b_n_n_l_o_mtaybnnlomytlmtu", "ref_code": "def main_solution(x):\n    return (func_13(x, '_') + (x + 'ytlmtu'))", "funcname": "main_solution"}
rule