code: def init_app(self, app):
          
          # If no version path was provided in the init of the Dockerflow
          # class we'll use the parent directory of the app root path.
          if self.version_path is None:
              self.version_path = os.path.dirname(app.root_path)
  
          for view in (
              ('/__version__', 'version', self._version_view),
              ('/__heartbeat__', 'heartbeat', self._heartbeat_view),
              ('/__lbheartbeat__', 'lbheartbeat', self._lbheartbeat_view),
          ):
              self._blueprint.add_url_rule(*view)
          self._blueprint.before_app_request(self._before_request)
          self._blueprint.after_app_request(self._after_request)
          self._blueprint.app_errorhandler(HeartbeatFailure)(self._heartbeat_exception_handler)
          app.register_blueprint(self._blueprint)
          got_request_exception.connect(self._got_request_exception, sender=app)
  
          if not hasattr(app, 'extensions'):  # pragma: nocover
              app.extensions = {}
          app.extensions['dockerflow'] = self
docs: Initializes the extension with the given app, registers the
          built-in views with an own blueprint and hooks up our signal
          callbacks.