You are given a code:

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

Can you predict the output of `main_solution("nkolwoi")` 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": "nkolwoi"}, "ref_output": "p_b_t_x_s_l_t_q", "ref_code": "def main_solution(x):\n    return func_13(func_20('ptst', 'bxlq'), '_')", "funcname": "main_solution"}
rule