You are given a code:

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

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