You are given a code:

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

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