code: def clean_up_inverse(self, current):
          
  
          if not self.inv_ext:
              return
  
          index = len(current) - 1
          while index >= 0:
              if isinstance(current[index], InvPlaceholder):
                  content = current[index + 1:]
                  content.append(_EOP if not self.pathname else self.path_eop)
                  current[index] = (''.join(content)) + (_EXCLA_GROUP_CLOSE % str(current[index]))
              index -= 1
          self.inv_ext = 0
docs: Clean up current.
  
          Python doesn't have variable lookbehinds, so we have to do negative lookaheads.
          !(...) when converted to regular expression is atomic, so once it matches, that's it.
          So we use the pattern `(?:(?!(?:stuff|to|exclude)<x>))[^/]*?)` where <x> is everything
          that comes after the negative group. `!(this|that)other` --> `(?:(?!(?:this|that)other))[^/]*?)`.
  
          We have to update the list before | in nested cases: *(!(...)|stuff). Before we close a parent
          `extmatch`: `*(!(...))`. And of course on path separators (when path mode is on): `!(...)/stuff`.
          Lastly we make sure all is accounted for when finishing the pattern at the end.  If there is nothing
          to store, we store `$`: `(?:(?!(?:this|that)$))[^/]*?)`.