You are given a code:

def main_solution(x):
    return (('tsm' + 'kow') + func_13('sprrax', '_'))

Can you predict the output of `main_solution("pxfntfnk")` 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": "pxfntfnk"}, "ref_output": "tsmkows_p_r_r_a_x", "ref_code": "def main_solution(x):\n    return (('tsm' + 'kow') + func_13('sprrax', '_'))", "funcname": "main_solution"}
rule