You are given a code:

def main_solution(x):
    return (func_13('zivkzt', '_') + ('pckt').swapcase())

Can you predict the output of `main_solution("pontfboq")` 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": "pontfboq"}, "ref_output": "z_i_v_k_z_tPCKT", "ref_code": "def main_solution(x):\n    return (func_13('zivkzt', '_') + ('pckt').swapcase())", "funcname": "main_solution"}
rule