import string
import random


def id_generator(size=6, chars=string.ascii_uppercase + string.digits):
    """
    Return random string of size
    @param size: int Length of returned string
    @param chars: list List of allowed chars
    @return: str Random string ex: "AJD45S"
    """
    return ''.join(random.choice(chars) for _ in range(size))