How to use the ptpython.validator.PythonValidator function in ptpython

# Set up a new completer and validator for the new grammar.
        g = self._create_grammar()

        self.completer = GrammarCompleter(g, completers={
            'enabled_breakpoint': BreakPointListCompleter(only_enabled=True),
            'disabled_breakpoint': BreakPointListCompleter(only_disabled=True),
            'alias_name': AliasCompleter(self),
            'python_code': PythonCompleter(lambda: self.curframe.f_globals, lambda: self.curframe.f_locals),
            'breakpoint': BreakPointListCompleter(),
            'pdb_command': PdbCommandsCompleter(self),
            'python_file': PythonFileCompleter(),
            'python_function': PythonFunctionCompleter(self),
        })
        self.validator = GrammarValidator(g, {
            'python_code': PythonValidator()
        })

        # Make sure not to start in Vi navigation mode.
        self.python_input.key_bindings_manager.reset(self.cli)
        self.cli.buffers[DEFAULT_BUFFER].reset()

        def pre_run():
            self._source_code_window.vertical_scroll = 100000 # source_code_doc.line_count

        try:
            return self.cli.run(reset_current_buffer=False, pre_run=pre_run).text
        except EOFError:
            # Turn Control-D key press into a 'quit' command.
            return 'quit'

# For internal use.
                 extra_key_bindings=None,
                 _completer=None, _validator=None,
                 _lexer=None, _extra_buffer_processors=None,
                 _extra_layout_body=None, _extra_toolbars=None,
                 _input_buffer_height=None):

        self.get_globals = get_globals or (lambda: {})
        self.get_locals = get_locals or self.get_globals

        self._completer = _completer or FuzzyCompleter(
            PythonCompleter(self.get_globals, self.get_locals,
                            lambda: self.enable_dictionary_completion),
            enable_fuzzy=Condition(lambda: self.enable_fuzzy_completion))
        self._validator = _validator or PythonValidator(self.get_compiler_flags)
        self._lexer = _lexer or PygmentsLexer(PythonLexer)

        if history_filename:
            self.history = ThreadedHistory(FileHistory(history_filename))
        else:
            self.history = InMemoryHistory()

        self._input_buffer_height = _input_buffer_height
        self._extra_layout_body = _extra_layout_body or []
        self._extra_toolbars = _extra_toolbars or []
        self._extra_buffer_processors = _extra_buffer_processors or []

        self.extra_key_bindings = extra_key_bindings or KeyBindings()

        # Settings.
        self.show_signature = False