# Buggy code
def create_application(self, full_layout=True):
    """makes the application object and the buffers"""
    layout_manager = LayoutManager(self)
    if full_layout:
        layout = layout_manager.create_layout(ExampleLexer, ToolbarLexer)
    else:
        layout = layout_manager.create_tutorial_layout()

    buffers = {
        DEFAULT_BUFFER: Buffer(is_multiline=True),
        "description": Buffer(is_multiline=True, read_only=True),
        "parameter": Buffer(is_multiline=True, read_only=True),
        "examples": Buffer(is_multiline=True, read_only=True),
        "bottom_toolbar": Buffer(is_multiline=True),
        "example_line": Buffer(is_multiline=True),
        "default_values": Buffer(),
        "symbols": Buffer(),
        "progress": Buffer(is_multiline=False),
    }

    writing_buffer = Buffer(
        history=self.history,
        auto_suggest=AutoSuggestFromHistory(),
        enable_history_search=True,
        completer=self.completer,
        complete_while_typing=Always(),
    )

    return Application(
        mouse_support=False,
        style=self.styles,
        buffer=writing_buffer,
        on_input_timeout=self.on_input_timeout,
        key_bindings_registry=InteractiveKeyBindings(self).registry,
        layout=layout,
        buffers=buffers,
    )


# Traceback (AssertionError)
(env36b) C:\Users\wilx\azure-cli>az interactive -s primary

Traceback (most recent call last):
File "C:\Users\wilx\azure-cli\env36b\lib\site-packages\knack\cli.py", line 194, in invoke
cmd_result = self.invocation.execute(args)
File "c:\users\wilx\azure-cli\src\azure-cli-core\azure\cli\core\commands\__init__.py", line 347, in execute
six.reraise(*sys.exc_info())
File "C:\Users\wilx\azure-cli\env36b\lib\site-packages\six.py", line 693, in reraise
raise value
File "c:\users\wilx\azure-cli\src\azure-cli-core\azure\cli\core\commands\__init__.py", line 319, in execute
result = cmd(params)
File "c:\users\wilx\azure-cli\src\azure-cli-core\azure\cli\core\commands\__init__.py", line 180, in __call__
return super(AzCliCommand, self).__call__(*args, **kwargs)
File "C:\Users\wilx\azure-cli\env36b\lib\site-packages\knack\commands.py", line 109, in __call__
return self.handler(*args, **kwargs)
File "c:\users\wilx\azure-cli\src\azure-cli-core\azure\cli\core\__init__.py", line 418, in default_command_handler
result = op(**command_args)
File "c:\users\wilx\azure-cli\src\command_modules\azure-cli-interactive\azure\cli\command_modules\interactive\__init__.py", line 13, in start_shell
AzInteractiveShell(cmd.cli_ctx, style)()
File "c:\users\wilx\azure-cli\src\command_modules\azure-cli-interactive\azure\cli\command_modules\interactive\azclishell\app.py", line 144, in __call__
self.run()
File "c:\users\wilx\azure-cli\src\command_modules\azure-cli-interactive\azure\cli\command_modules\interactive\azclishell\app.py", line 690, in run
self.cli.buffers['symbols'].reset(
File "c:\users\wilx\azure-cli\src\command_modules\azure-cli-interactive\azure\cli\command_modules\interactive\azclishell\app.py", line 151, in cli
self._cli = self.create_interface()
File "c:\users\wilx\azure-cli\src\command_modules\azure-cli-interactive\azure\cli\command_modules\interactive\azclishell\app.py", line 369, in create_interface
application=self.create_application(),
File "c:\users\wilx\azure-cli\src\command_modules\azure-cli-interactive\azure\cli\command_modules\interactive\azclishell\app.py", line 362, in create_application
buffers=buffers,
File "C:\Users\wilx\azure-cli\env36b\lib\site-packages\prompt_toolkit\application.py", line 121, in __init__
assert style is None or isinstance(style, Style)
AssertionError

# Fixed code
def create_application(self, full_layout=True):
    """makes the application object and the buffers"""
    layout_manager = LayoutManager(self)
    if full_layout:
        layout = layout_manager.create_layout(ExampleLexer, ToolbarLexer)
    else:
        layout = layout_manager.create_tutorial_layout()

    buffers = {
        DEFAULT_BUFFER: Buffer(is_multiline=True),
        "description": Buffer(is_multiline=True, read_only=True),
        "parameter": Buffer(is_multiline=True, read_only=True),
        "examples": Buffer(is_multiline=True, read_only=True),
        "bottom_toolbar": Buffer(is_multiline=True),
        "example_line": Buffer(is_multiline=True),
        "default_values": Buffer(),
        "symbols": Buffer(),
        "progress": Buffer(is_multiline=False),
    }

    writing_buffer = Buffer(
        history=self.history,
        auto_suggest=AutoSuggestFromHistory(),
        enable_history_search=True,
        completer=self.completer,
        complete_while_typing=Always(),
    )

    return Application(
        mouse_support=False,
        style=self.style,
        buffer=writing_buffer,
        on_input_timeout=self.on_input_timeout,
        key_bindings_registry=InteractiveKeyBindings(self).registry,
        layout=layout,
        buffers=buffers,
    )