You are given a code:

def main_solution(x):
    return func_20(func_15('upmtg'), func_4('nxysm'))

Can you predict the output of `main_solution("sba")` 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": "sba"}, "ref_output": "\u00abnux\u00bby\u00abspm\u00bb\u00abm\u00bb\u00abt\u00bb\u00abg\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15('upmtg'), func_4('nxysm'))", "funcname": "main_solution"}
rule