You are given a code:

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

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