You are given a code:

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

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