You are given a code:

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

Can you predict the output of `main_solution("yfdpmq")` 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": "yfdpmq"}, "ref_output": "\u00ab\u00abyv\u00bb\u00bb\u00ab\u00abfp\u00bb\u00bb\u00ab\u00abdx\u00bb\u00bb\u00ab\u00abpb\u00bb\u00bb\u00ab\u00abmk\u00bb\u00bb\u00ab\u00abqa\u00bb\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15(x), func_15('vpxbka'))", "funcname": "main_solution"}
rule