def join_string(list_string, join_string):
    """
    Join string based on join_string

    Parameters
    ----------
    list_string : string list
        list of string to be join
    join_string : string
        characters used for the joining

    Returns
    -------
    string joined : string
        a string where all elements of the list string have been join with join_string between them

    Examples
    --------
    >>> test = ["a", "b", "c", "d"]
    >>> join_string(test, "/")
    'a/b/c/d'
    """
    return join_string.join(list_string)