How to use the h11._util.LocalProtocolError function in h11

def _obsolete_line_fold(lines):
    it = iter(lines)
    last = None
    for line in it:
        match = obs_fold_re.match(line)
        if match:
            if last is None:
                raise LocalProtocolError("continuation line at start of headers")
            if not isinstance(last, bytearray):
                last = bytearray(last)
            last += b" "
            last += line[match.end() :]
        else:
            if last is not None:
                yield last
            last = line
    if last is not None:
        yield last

def validate(regex, data, msg="malformed data", *format_args):
    match = _fullmatch(regex, data)
    if not match:
        if format_args:
            msg = msg.format(*format_args)
        raise LocalProtocolError(msg)
    return match.groupdict()

def _fire_event_triggered_transitions(self, role, event_type):
        state = self.states[role]
        try:
            new_state = EVENT_TRIGGERED_TRANSITIONS[role][state][event_type]
        except KeyError:
            raise LocalProtocolError(
                "can't handle event type {} when role={} and state={}".format(
                    event_type.__name__, role, self.states[role]
                )
            )
        self.states[role] = new_state

def send_with_data_passthrough(self, event):
        """Identical to :meth:`send`, except that in situations where
        :meth:`send` returns a single :term:`bytes-like object`, this instead
        returns a list of them -- and when sending a :class:`Data` event, this
        list is guaranteed to contain the exact object you passed in as
        :attr:`Data.data`. See :ref:`sendfile` for discussion.

        """
        if self.our_state is ERROR:
            raise LocalProtocolError("Can't send data when our state is ERROR")
        try:
            if type(event) is Response:
                self._clean_up_response_headers_for_sending(event)
            # We want to call _process_event before calling the writer,
            # because if someone tries to do something invalid then this will
            # give a sensible error message, while our writers all just assume
            # they will only receive valid events. But, _process_event might
            # change self._writer. So we have to do a little dance:
            writer = self._writer
            self._process_event(self.our_role, event)
            if type(event) is ConnectionClosed:
                return None
            else:
                # In any situation where writer is None, process_event should
                # have raised ProtocolError
                assert writer is not None

def send_data(self, data, write):
        self._length -= len(data)
        if self._length < 0:
            raise LocalProtocolError("Too much data for declared Content-Length")
        write(data)

def send_eom(self, headers, write):
        if self._length != 0:
            raise LocalProtocolError("Too little data for declared Content-Length")
        if headers:
            raise LocalProtocolError("Content-Length and trailers don't mix")

validate(_content_length_re, value, "bad Content-Length")
            saw_content_length = True
        if name == b"transfer-encoding":
            # "A server that receives a request message with a transfer coding
            # it does not understand SHOULD respond with 501 (Not
            # Implemented)."
            # https://tools.ietf.org/html/rfc7230#section-3.3.1
            if saw_transfer_encoding:
                raise LocalProtocolError(
                    "multiple Transfer-Encoding headers", error_status_hint=501
                )
            # "All transfer-coding names are case-insensitive"
            # -- https://tools.ietf.org/html/rfc7230#section-4
            value = value.lower()
            if value != b"chunked":
                raise LocalProtocolError(
                    "Only Transfer-Encoding: chunked is supported",
                    error_status_hint=501,
                )
            saw_transfer_encoding = True
        new_headers.append((name, value))
    return new_headers

def _validate(self):
        if not (100 <= self.status_code < 200):
            raise LocalProtocolError(
                "InformationalResponse status_code should be in range "
                "[100, 200), not {}".format(self.status_code)
            )

value = bytesify(value)
            validate(_field_name_re, name, "Illegal header name {!r}", name)
            validate(_field_value_re, value, "Illegal header value {!r}", value)
        name = name.lower()
        if name == b"content-length":
            if saw_content_length:
                raise LocalProtocolError("multiple Content-Length headers")
            validate(_content_length_re, value, "bad Content-Length")
            saw_content_length = True
        if name == b"transfer-encoding":
            # "A server that receives a request message with a transfer coding
            # it does not understand SHOULD respond with 501 (Not
            # Implemented)."
            # https://tools.ietf.org/html/rfc7230#section-3.3.1
            if saw_transfer_encoding:
                raise LocalProtocolError(
                    "multiple Transfer-Encoding headers", error_status_hint=501
                )
            # "All transfer-coding names are case-insensitive"
            # -- https://tools.ietf.org/html/rfc7230#section-4
            value = value.lower()
            if value != b"chunked":
                raise LocalProtocolError(
                    "Only Transfer-Encoding: chunked is supported",
                    error_status_hint=501,
                )
            saw_transfer_encoding = True
        new_headers.append((name, value))
    return new_headers