<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _slug_strip(self, value):
 """ Clean 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. """

        re_sep = '(?:-|%s)' % re.escape(self.separator)
        value = re.sub('%s+' % re_sep, self.separator, value)
        return re.sub(r'^%s+|%s+$' % (re_sep, re_sep), '', value)