def add_leading_zeros(input_string: str, out_len: int) -> str:
    """This function adds leading zeros to the input string. The output string will have length == out_len
    Args:
        input_string (str): the input string
        out_len (int): length of output string with leading zeros
    Returns:
        out_string (str): the initial string but wiht leading zeros up to out_len characters
    """
    out_string = input_string.zfill(out_len)
    
    return out_string