How to use the xblock.core.XBlock.load_class function in XBlock

def settings(request):

    blocks = {
        'edx/test/verticala': XBlock.load_class('vertical')(DebuggerRuntime(), {}, {}, {}, {}),
        'edx/test/verticalb': XBlock.load_class('vertical')(DebuggerRuntime(), {}, {}, {}, {}),
    }

    course_usages = Usage('course', 'edx/test/course', {
        'graded': True,
        'start_date': '1/2/12',
    }, [
        Usage('verticala', 'edx/test/verticala', {}, []),
        Usage('verticalb', 'edx/test/verticalb', {}, [])
    ]).as_json()

    course = XBlock.load_class('course')(DebuggerRuntime(), {
            'policy_list': [{'class': 'cascade', 'params': {'keys': ['graded']}}],
            'usage_tree': course_usages,
        }, {}, {}, {})

def settings(request):

    blocks = {
        'edx/test/verticala': XBlock.load_class('vertical')(DebuggerRuntime(), {}, {}, {}, {}),
        'edx/test/verticalb': XBlock.load_class('vertical')(DebuggerRuntime(), {}, {}, {}, {}),
    }

    course_usages = Usage('course', 'edx/test/course', {
        'graded': True,
        'start_date': '1/2/12',
    }, [
        Usage('verticala', 'edx/test/verticala', {}, []),
        Usage('verticalb', 'edx/test/verticalb', {}, [])
    ]).as_json()

    course = XBlock.load_class('course')(DebuggerRuntime(), {
            'policy_list': [{'class': 'cascade', 'params': {'keys': ['graded']}}],
            'usage_tree': course_usages,
        }, {}, {}, {})

    return render_to_response('settings.html', {

def get(self, block_type, resource):
        xblock_class = xblock.core.XBlock.load_class(block_type)

        mimetype = mimetypes.guess_type(resource)[0]
        if mimetype is None:
            mimetype = 'application/octet-stream'

        self.response.status = 200
        self.response.headers['Content-Type'] = mimetype
        self.response.cache_control.no_cache = None
        self.response.cache_control.public = 'public'
        self.response.cache_control.max_age = 600
        self.response.write(xblock_class.open_local_resource(resource).read())

def load_block_type(self, block_type):
        """
        Returns a subclass of :class:`.XBlock` that corresponds to the specified `block_type`.
        """
        return XBlock.load_class(block_type, self.default_class, self.select)

def package_resource(_request, block_type, resource):
    """
    Wrapper for `pkg_resources` that tries to access a resource and, if it
    is not found, raises an Http404 error.
    """
    try:
        xblock_class = XBlock.load_class(block_type)
        content = xblock_class.open_local_resource(resource)
    except Exception:  # pylint: disable-msg=broad-except
        raise Http404
    mimetype, _ = mimetypes.guess_type(resource)
    return HttpResponse(content, mimetype=mimetype)

def settings(request):

    blocks = {
        'edx/test/verticala': XBlock.load_class('vertical')(DebuggerRuntime(), {}, {}, {}, {}),
        'edx/test/verticalb': XBlock.load_class('vertical')(DebuggerRuntime(), {}, {}, {}, {}),
    }

    course_usages = Usage('course', 'edx/test/course', {
        'graded': True,
        'start_date': '1/2/12',
    }, [
        Usage('verticala', 'edx/test/verticala', {}, []),
        Usage('verticalb', 'edx/test/verticalb', {}, [])
    ]).as_json()

    course = XBlock.load_class('course')(DebuggerRuntime(), {
            'policy_list': [{'class': 'cascade', 'params': {'keys': ['graded']}}],
            'usage_tree': course_usages,
        }, {}, {}, {})

    return render_to_response('settings.html', {
        'base_tree': json.dumps(course.usage_tree.as_json(), indent=4),
        'applied_tree': json.dumps(course.apply_policies(User()).as_json(), indent=4),
    })