You are given a code:

def main_solution(x):
    return func_20(func_15('mkfq'), (x + 'xibvta'))

Can you predict the output of `main_solution("fqxssko")` 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": "fqxssko"}, "ref_output": "\u00abfmq\u00bbx\u00absks\u00bbk\u00abofx\u00bbi\u00abbqv\u00bbta", "ref_code": "def main_solution(x):\n    return func_20(func_15('mkfq'), (x + 'xibvta'))", "funcname": "main_solution"}
rule