You are given a code:

def main_solution(x):
    return func_20(func_15('lpretj'), func_1('bts', 4))

Can you predict the output of `main_solution("gdxkhkfg")` 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": "gdxkhkfg"}, "ref_output": "\u00abblt\u00bbs\u00abbpt\u00bbs\u00abbrt\u00bbs\u00abbet\u00bbs\u00abt\u00bb\u00abj\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15('lpretj'), func_1('bts', 4))", "funcname": "main_solution"}
rule