You are given a code:

def main_solution(x):
    return func_20(func_15('spqbv'), func_15(x))

Can you predict the output of `main_solution("qacaobz")` 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": "qacaobz"}, "ref_output": "\u00ab\u00absq\u00bb\u00bb\u00ab\u00abpa\u00bb\u00bb\u00ab\u00abqc\u00bb\u00bb\u00ab\u00abba\u00bb\u00bb\u00ab\u00abvo\u00bb\u00bb\u00abb\u00bb\u00abz\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15('spqbv'), func_15(x))", "funcname": "main_solution"}
rule