code: def filter_string(self, word):
          
          segs = [m.group(0) for m in self.seg_regex.finditer(word)]
          return ''.join(segs)
docs: Return a string like the input but containing only legal IPA segments
  
          Args:
              word (unicode): input string to be filtered
  
          Returns:
              unicode: string identical to `word` but with invalid IPA segments
                       absent