def registrations_with_user_id(self,user_id: str) -> RegistrationsWithUserIdRequestBuilder:
        """
        Provides operations to manage the registrations property of the microsoft.graph.virtualEventWebinar entity.
        param user_id: Alternate key of virtualEventRegistration
        Returns: RegistrationsWithUserIdRequestBuilder
        """
        if user_id is None:
            raise TypeError("user_id cannot be null.")
        from .registrations_with_user_id.registrations_with_user_id_request_builder import RegistrationsWithUserIdRequestBuilder

        return RegistrationsWithUserIdRequestBuilder(self.request_adapter, self.path_parameters, user_id)

        Provides operations to manage the registrations property of the microsoft.graph.virtualEventWebinar entity.
        param user_id: Alternate key of virtualEventRegistration
        Returns: RegistrationsWithUserIdRequestBuilder
        
msgraph/generated/solutions/virtual_events/webinars/item/virtual_event_webinar_item_request_builder.py