You are given a code:

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

Can you predict the output of `main_solution("yvgpidb")` 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": "yvgpidb"}, "ref_output": "y\u00abytv\u00bbv\u00abgcg\u00bbp\u00abpwi\u00bbi\u00abddd\u00bbbb", "ref_code": "def main_solution(x):\n    return func_20(func_20(x, x), func_15('tcwd'))", "funcname": "main_solution"}
rule