You are given a code:

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

Can you predict the output of `main_solution("yfrqu")` 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": "yfrqu"}, "ref_output": "y\u00abfxr\u00bbq\u00abuxy\u00bbf\u00abrcq\u00bbu\u00abx\u00bb", "ref_code": "def main_solution(x):\n    return func_20((x + x), func_15('xxcx'))", "funcname": "main_solution"}
rule