def METHOD_NAME(buf):
    """
    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.
    """
    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