def _prep_vars(variables: list):
    """
    Convert from a list to a comma separated string

    :param variables: list of vars
    :return: comma separated string
    """

    # if vars is not a string, assume it's a list of multiple strings
    out = ""
    for i in range(len(variables) - 1):
        out += variables[i]
        out += ","

    out += variables[-1]

    return out