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Complete this python program:
def _validate_format(format, alternative):
assistant
#Here is the Python code you requested.

    """Test format string `alternative` against `format`.  `format` can be the
    msgid of a message and `alternative` one of the `msgstr`\s.  The two
    arguments are not interchangeable as `alternative` may contain less
    placeholders if `format` uses named placeholders.
    The behavior of this function is undefined if the string does not use
    string formattings.
    If the string formatting of `alternative` is compatible to `format` the
    function returns `None`, otherwise a `TranslationError` is raised.
    Examples for compatible format strings:
    >>> _validate_format(\Hello %s!\, \Hallo %s!\)
    >>> _validate_format(\Hello %i!\, \Hallo %d!\)
    Example for an incompatible format strings:
    >>> _validate_format(\Hello %(name)s!\, \Hallo %s!\)
    Traceback (most recent call last):
    TranslationError: the format strings are of different kinds
    This function is used by the `python_format` checker.
    :param format: The original format string
    :param alternative: The alternative format string that should be checked
    against format
    :return: None on success
    :raises TranslationError: on formatting errors
    """
    def _parse(string):
        result = []
        for match in PYTHON_FORMAT.finditer(string):
            (name, format, typechar) = match.groups()
            if ((typechar == '%') and (name is None)):
                continue
            result.append((name, str(typechar)))
        return result
    def _compatible(a, b):
        if (a == b):
            return True
        for set in _string_format_compatibilities:
            if ((a in set) and (b in set)):
                return True
        return False
    def _check_positional(results):
        positional = None
        for (name, char) in results:
            if (positional is None):
                positional = (name is None)
            elif ((name is None) != positional):
                raise TranslationError('format    string    mixes    positional    and    named    placeholders')
        return bool(positional)
    (a, b) = map(_parse, (format, alternative))
    (a_positional, b_positional) = map(_check_positional, (a, b))
    if (a_positional and (not b_positional) and (not b)):
        raise TranslationError('placeholders    are    incompatible')
    elif (a_positional != b_positional):
        raise TranslationError('the    format    strings    are    of    different    kinds')
    if a_positional:
        if (len(a) != len(b)):
            raise TranslationError('positional    format    placeholders    are    unbalanced')
        for (idx, ((_, first), (_, second))) in enumerate(izip(a, b)):
            if (not _compatible(first, second)):
                raise TranslationError(('incompatible    format    for    placeholder    %d:    %r    and    %r    are    not    compatible' % ((idx + 1), first, second)))
    else:
        type_map = dict(a)
        for (name, typechar) in b:
            if (name not in type_map):
                raise TranslationError(('unknown    named    placeholder    %r' % name))
            elif (not _compatible(typechar, type_map[name])):
                raise TranslationError(('incompatible    format    for  ...