You are given a code:

def main_solution(x):
    return func_13(func_20('nryy', x), '_')

Can you predict the output of `main_solution("nyvpjkltte")` 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": "nyvpjkltte"}, "ref_output": "n_n_r_y_y_v_y_p_j_k_l_t_t_e", "ref_code": "def main_solution(x):\n    return func_13(func_20('nryy', x), '_')", "funcname": "main_solution"}
rule