def update_parameter(old_parameter, new_parameter):
    """
    Works as the 'update' of dictionnaries but instead of replacing a list
    by another one, this method add each element of a list to the other by
    skipping duplicate.
    """
    for key in new_parameter:
        if key in old_parameter:
            if isinstance(old_parameter[key], list):
                for string_ in new_parameter[key]:
                    if string_ not in old_parameter[key]:
                        old_parameter[key].append(string_)
            else:
                old_parameter[key] = new_parameter[key]
        else:
            old_parameter[key] = new_parameter[key]
