How to use the ijson.backends.python.UnexpectedSymbol function in ijson

def parse_array(lexer):
    yield ('start_array', None)
    try:
        pos, symbol = next(lexer)
        if symbol != ']':
            while True:
                for event in parse_value(lexer, symbol, pos):
                    yield event
                pos, symbol = next(lexer)
                if symbol == ']':
                    break
                if symbol != ',':
                    raise UnexpectedSymbol(symbol, pos)
                pos, symbol = next(lexer)
        yield ('end_array', None)
    except StopIteration:
        raise common.IncompleteJSONError('Incomplete JSON data')

yield ('boolean', True)
        elif symbol == 'false':
            yield ('boolean', False)
        elif symbol == '[':
            for event in parse_array(lexer):
                yield event
        elif symbol == '{':
            for event in parse_object(lexer):
                yield event
        elif symbol[0] == '"':
            yield ('string', unescape(symbol[1:-1]))
        else:
            try:
                yield ('number', common.number(symbol))
            except decimal.InvalidOperation:
                raise UnexpectedSymbol(symbol, pos)
    except StopIteration:
        raise common.IncompleteJSONError('Incomplete JSON data')

def __init__(self, symbol, pos):
        super(UnexpectedSymbol, self).__init__(
            'Unexpected symbol %r at %d' % (symbol, pos)
        )

def parse_object(lexer):
    yield ('start_map', None)
    try:
        pos, symbol = next(lexer)
        if symbol != '}':
            while True:
                if symbol[0] != '"':
                    raise UnexpectedSymbol(symbol, pos)
                yield ('map_key', unescape(symbol[1:-1]))
                pos, symbol = next(lexer)
                if symbol != ':':
                    raise UnexpectedSymbol(symbol, pos)
                for event in parse_value(lexer, None, pos):
                    yield event
                pos, symbol = next(lexer)
                if symbol == '}':
                    break
                if symbol != ',':
                    raise UnexpectedSymbol(symbol, pos)
                pos, symbol = next(lexer)
        yield ('end_map', None)
    except StopIteration:
        raise common.IncompleteJSONError('Incomplete JSON data')