code: def filter_international_words(buf):
          
          filtered = bytearray()
  
          # This regex expression filters out only words that have at-least one
          # international character. The word may include one marker character at
          # the end.
          words = re.findall(b'[a-zA-Z]*[\x80-\xFF]+[a-zA-Z]*[^a-zA-Z\x80-\xFF]?',
                             buf)
  
          for word in words:
              filtered.extend(word[:-1])
  
              # If the last character in the word is a marker, replace it with a
              # space as markers shouldn't affect our analysis (they are used
              # similarly across all languages and may thus have similar
              # frequencies).
              last_char = word[-1:]
              if not last_char.isalpha() and last_char < b'\x80':
                  last_char = b' '
              filtered.extend(last_char)
  
          return filtered
docs: We define three types of bytes:
          alphabet: english alphabets [a-zA-Z]
          international: international characters [\x80-\xFF]
          marker: everything else [^a-zA-Z\x80-\xFF]
  
          The input buffer can be thought to contain a series of words delimited
          by markers. This function works to filter all words that contain at
          least one international character. All contiguous sequences of markers
          are replaced by a single space ascii character.
  
          This filter applies to all scripts which do not use English characters.