def prepend_or_set(config, section, option, value, defaults):
    """
    If option is already set, then value is prepended.
    If option is not set, then it is created and set to value.
    This is used to prepend options with values which come from the module documentation.
    """
    if value:
        if config.has_option(section, option):
            value += '\n%s' % config.get(section, option, 0, defaults)
        config.set(section, option, value)
    return config