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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _slug_strip(value, separator='-'):
 """ Cleans up a slug by removing slug separator characters that occur at the beginning or end of a slug. If an alternate separator is used, it will also replace any instances of the default '-' separator with the new separator. """

    separator = separator or ''
    if separator == '-' or not separator:
        re_sep = '-'
    else:
        re_sep = '(?:-|%s)' % re.escape(separator)
    # Remove multiple instances and if an alternate separator is provided,
    # replace the default '-' separator.
    if separator != re_sep:
        value = re.sub('%s+' % re_sep, separator, value)
    # Remove separator from the beginning and end of the slug.
    if separator:
        if separator != '-':
            re_sep = re.escape(separator)
        value = re.sub(r'^%s+|%s+$' % (re_sep, re_sep), '', value)
    return value