You are given a code:

def main_solution(x):
    return (func_13(x, '_') + (x + 'syo'))

Can you predict the output of `main_solution("eqrursfknu")` 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": "eqrursfknu"}, "ref_output": "e_q_r_u_r_s_f_k_n_ueqrursfknusyo", "ref_code": "def main_solution(x):\n    return (func_13(x, '_') + (x + 'syo'))", "funcname": "main_solution"}
rule