class RequestHandler(object):"""Base class for HTTP request handlers.
Subclasses must define at least one of the methods defined in the"Entry points" section below."""
    SUPPORTED_METHODS = ("GET", "HEAD", "POST", "DELETE", "PATCH", "PUT","OPTIONS")_template_loaders = {}  # type: typing.Dict[str, template.BaseLoader]_template_loader_lock = threading.Lock()_remove_control_chars_regex = re.compile(r"[\x00-\x08\x0e-\x1f]")def __init__(self, application, request, **kwargs):super(RequestHandler, self).__init__()self.application = applicationself.request = requestself._headers_written = Falseself._finished = Falseself._auto_finish = Trueself._transforms = None  # will be set in _executeself._prepared_future = Noneself._headers = None  # type: httputil.HTTPHeadersself.path_args = Noneself.path_kwargs = Noneself.ui = ObjectDict((n, self._ui_method(m)) for n, m inapplication.ui_methods.items())# UIModules are available as both `modules` and `_tt_modules` in the# template namespace.  Historically only `modules` was available# but could be clobbered by user additions to the namespace.# The template {% module %} directive looks in `_tt_modules` to avoid# possible conflicts.self.ui["_tt_modules"] = _UIModuleNamespace(self,application.ui_modules)self.ui["modules"] = self.ui["_tt_modules"]self.clear()self.request.connection.set_close_callback(self.on_connection_close)self.initialize(**kwargs)

    def initialize(self):"""Hook for subclass initialization. Called for each request.
A dictionary passed as the third argument of a url spec will besupplied as keyword arguments to initialize().Example::class ProfileHandler(RequestHandler):def initialize(self, database):self.database = databasedef get(self, username):...app = Application([(r'/user/(.*)', ProfileHandler, dict(database=database)),])"""
        pass