You are given a code:

def main_solution(x):
    return func_13(func_20('bvst', 'xhwfeo'), '_')

Can you predict the output of `main_solution("mlyeczguae")` 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": "mlyeczguae"}, "ref_output": "b_x_v_h_s_w_t_f_e_o", "ref_code": "def main_solution(x):\n    return func_13(func_20('bvst', 'xhwfeo'), '_')", "funcname": "main_solution"}
rule