You are given a code:

def main_solution(x):
    return func_9(func_13('bpvkos', '_'))

Can you predict the output of `main_solution("jbbqlrurm")` 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": "jbbqlrurm"}, "ref_output": "b_p_v_k_o_ss_o_k_v_p_b", "ref_code": "def main_solution(x):\n    return func_9(func_13('bpvkos', '_'))", "funcname": "main_solution"}
rule