You are given a code:

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

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