def _tweak_prefix(prefix):
    """ If a prefix or regex ends with '_-', change it to end with '-' instead.

    Args:
        prefix (str): Prefix that might need tweaking.

    Returns:
        (str) Prefix that has been tweaked if it needed to.
    """
    if prefix.endswith('_-'):
        prefix = prefix.rstrip('_-') + '-'
    return prefix