You are given a code:

def main_solution(x):
    return func_20(func_15('rfwl'), (x + 'obb'))

Can you predict the output of `main_solution("vkwuqi")` 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": "vkwuqi"}, "ref_output": "\u00abvrk\u00bbw\u00abufq\u00bbi\u00abowb\u00bbb\u00abl\u00bb", "ref_code": "def main_solution(x):\n    return func_20(func_15('rfwl'), (x + 'obb'))", "funcname": "main_solution"}
rule