You are given a code:

def main_solution(x):
    return func_22(func_4('apqvdb'))

Can you predict the output of `main_solution("pldkm")` 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": "pldkm"}, "ref_output": "apqvdb", "ref_code": "def main_solution(x):\n    return func_22(func_4('apqvdb'))", "funcname": "main_solution"}
rule