You are given a code:

def main_solution(x):
    return func_4(func_4('trrso'))

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