You are given a code:

def main_solution(x):
    return func_9(func_13('sbtx', '_'))

Can you predict the output of `main_solution("xqsxrxw")` 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": "xqsxrxw"}, "ref_output": "s_b_t_xx_t_b_s", "ref_code": "def main_solution(x):\n    return func_9(func_13('sbtx', '_'))", "funcname": "main_solution"}
rule