You are given a code:

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

Can you predict the output of `main_solution("exerebcixn")` 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": "exerebcixn"}, "ref_output": "e\u00abxge\u00bbr\u00abebb\u00bbc\u00abixx\u00bbn\u00abn\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_4(x), func_15('gbxn'))", "funcname": "main_solution"}
rule