You are given a code:

def main_solution(x):
    return func_4(func_20('yspwi', 'vbe'))

Can you predict the output of `main_solution("imbba")` 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": "imbba"}, "ref_output": "yvsbpewi", "ref_code": "def main_solution(x):\n    return func_4(func_20('yspwi', 'vbe'))", "funcname": "main_solution"}
rule