You are given a code:

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

Can you predict the output of `main_solution("eumus")` 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": "eumus"}, "ref_output": "h_g_k_u_t_g_e_t_q_g_x_y", "ref_code": "def main_solution(x):\n    return func_13(('hgkutg' + 'etqgxy'), '_')", "funcname": "main_solution"}
rule