How to use the dtale.utils.get_host function in dtale

def test_get_host():
    with mock.patch('socket.gethostname', mock.Mock(return_value='test')),\
            mock.patch('socket.gethostbyname', mock.Mock(return_value='127.0.0.1')):
        assert utils.get_host() == 'test'
    with mock.patch('socket.gethostbyname', mock.Mock(return_value='127.0.0.1')):
        assert utils.get_host('test') == 'test'
    with mock.patch('socket.gethostname', mock.Mock(return_value='http://test')),\
            mock.patch('socket.gethostbyname', mock.Mock(side_effect=Exception)):
        assert utils.get_host() == 'localhost'
    with mock.patch('socket.gethostbyname', mock.Mock(side_effect=Exception)):
        with pytest.raises(Exception) as error:
            utils.get_host('test')
        assert str(error.value).startswith('Hostname (test) is not recognized')

compress = Compress()
    compress.init_app(app)

    _, version = retrieve_meta_info_and_version('dtale')
    template = dict(
        info={
            'title': 'D-Tale',
            'version': version,
            'description': 'Web Client for Visualizing Pandas Objects',
            'contact': {
                'name': 'Man Alpha Technology',
                'email': 'ManAlphaTech@man.com',
                'url': 'https://github.com/man-group/dtale'
            },
        },
        host=get_host(host),
        schemes=['http'],
    )
    try:
        from flasgger import Swagger  # flake8: NOQA
        Swagger(app, template=template)
    except ImportError:
        logger.debug('flasgger dependency not found, please install to enable feature')

    @app.route('/')
    @app.route('/dtale')
    @swag_from('swagger/dtale/root.yml')
    def root():
        """
        :class:`flask:flask.Flask` routes which redirect to dtale/main

        :return: 302 - flask.redirect('/dtale/main')

:class:`flask:flask.Flask` process

    :param host: hostname to use otherwise it will default to the output of :func:`python:socket.gethostname`
    :type host: str, optional
    :param port: port to use otherwise default to the output of :func:dtale.app.find_free_port
    :type port: str, optional
    :param force: boolean flag to determine whether to ignore the :func:dtale.app.find_free_port function
    :type force: bool
    :return:
    """
    global ACTIVE_HOST, ACTIVE_PORT

    if force:
        active_host = get_host(ACTIVE_HOST)
        curr_base = build_url(ACTIVE_PORT, active_host)
        final_host = get_host(host)
        new_base = build_url(port, final_host)
        if curr_base != new_base:
            if is_up(new_base):
                try:
                    kill(new_base)  # kill the original process
                except BaseException:
                    raise IOError((
                        'Could not kill process at {}, possibly something else is running at port {}. Please try '
                        'another port.'
                    ).format(new_base, port))
                while is_up(new_base):
                    time.sleep(0.01)
            ACTIVE_HOST = final_host
            ACTIVE_PORT = port
            return

if is_up(new_base):
                try:
                    kill(new_base)  # kill the original process
                except BaseException:
                    raise IOError((
                        'Could not kill process at {}, possibly something else is running at port {}. Please try '
                        'another port.'
                    ).format(new_base, port))
                while is_up(new_base):
                    time.sleep(0.01)
            ACTIVE_HOST = final_host
            ACTIVE_PORT = port
            return

    if ACTIVE_HOST is None:
        ACTIVE_HOST = get_host(host)

    if ACTIVE_PORT is None:
        ACTIVE_PORT = int(port or find_free_port())

"""
    Helper function to initalize global state corresponding to the host & port being used for your
    :class:`flask:flask.Flask` process

    :param host: hostname to use otherwise it will default to the output of :func:`python:socket.gethostname`
    :type host: str, optional
    :param port: port to use otherwise default to the output of :func:dtale.app.find_free_port
    :type port: str, optional
    :param force: boolean flag to determine whether to ignore the :func:dtale.app.find_free_port function
    :type force: bool
    :return:
    """
    global ACTIVE_HOST, ACTIVE_PORT

    if force:
        active_host = get_host(ACTIVE_HOST)
        curr_base = build_url(ACTIVE_PORT, active_host)
        final_host = get_host(host)
        new_base = build_url(port, final_host)
        if curr_base != new_base:
            if is_up(new_base):
                try:
                    kill(new_base)  # kill the original process
                except BaseException:
                    raise IOError((
                        'Could not kill process at {}, possibly something else is running at port {}. Please try '
                        'another port.'
                    ).format(new_base, port))
                while is_up(new_base):
                    time.sleep(0.01)
            ACTIVE_HOST = final_host
            ACTIVE_PORT = port