You are given a code:

def main_solution(x):
    return (func_15(x) + func_13('twfvll', '_'))

Can you predict the output of `main_solution("tjgkgdy")` 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": "tjgkgdy"}, "ref_output": "\u00abt\u00bb\u00abj\u00bb\u00abg\u00bb\u00abk\u00bb\u00abg\u00bb\u00abd\u00bb\u00aby\u00bbt_w_f_v_l_l", "ref_code": "def main_solution(x):\n    return (func_15(x) + func_13('twfvll', '_'))", "funcname": "main_solution"}
rule