How to use the river.core.workflowregistry.workflow_registry function in river

def contribute_to_class(self, cls, name):
        @classproperty
        def river(_self):
            return RiverObject(_self)

        self.field_name = name

        self._add_to_class(cls, self.field_name + "_transition_approvals", GenericRelation('%s.%s' % (TransitionApproval._meta.app_label, TransitionApproval._meta.object_name)))
        self._add_to_class(cls, self.field_name + "_transitions", GenericRelation('%s.%s' % (Transition._meta.app_label, Transition._meta.object_name)))

        if id(cls) not in workflow_registry.workflows:
            self._add_to_class(cls, "river", river)

        super(StateField, self).contribute_to_class(cls, name)

        if id(cls) not in workflow_registry.workflows:
            post_save.connect(_on_workflow_object_saved, self.model, False, dispatch_uid='%s_%s_riverstatefield_post' % (self.model, name))
            post_delete.connect(_on_workflow_object_deleted, self.model, False, dispatch_uid='%s_%s_riverstatefield_post' % (self.model, name))

        workflow_registry.add(self.field_name, cls)

def _register_hook_inlines(self, model):  # pylint: disable=no-self-use
        from django.contrib import admin
        from river.core.workflowregistry import workflow_registry
        from river.admin import OnApprovedHookInline, OnTransitHookInline, OnCompleteHookInline, DefaultWorkflowModelAdmin

        registered_admin = admin.site._registry.get(model, None)
        if registered_admin:
            if OnApprovedHookInline not in registered_admin.inlines:
                registered_admin.inlines = list(set(registered_admin.inlines + [OnApprovedHookInline, OnTransitHookInline, OnCompleteHookInline]))
                registered_admin.readonly_fields = list(set(list(registered_admin.readonly_fields) + list(workflow_registry.get_class_fields(model))))
                admin.site._registry[model] = registered_admin
        else:
            admin.site.register(model, DefaultWorkflowModelAdmin)

def _get_all_workflow_fields(cls):
        from river.core.workflowregistry import workflow_registry
        return reduce(operator.concat, map(list, workflow_registry.workflows.values()), [])

self.field_name = name

        self._add_to_class(cls, self.field_name + "_transition_approvals", GenericRelation('%s.%s' % (TransitionApproval._meta.app_label, TransitionApproval._meta.object_name)))
        self._add_to_class(cls, self.field_name + "_transitions", GenericRelation('%s.%s' % (Transition._meta.app_label, Transition._meta.object_name)))

        if id(cls) not in workflow_registry.workflows:
            self._add_to_class(cls, "river", river)

        super(StateField, self).contribute_to_class(cls, name)

        if id(cls) not in workflow_registry.workflows:
            post_save.connect(_on_workflow_object_saved, self.model, False, dispatch_uid='%s_%s_riverstatefield_post' % (self.model, name))
            post_delete.connect(_on_workflow_object_deleted, self.model, False, dispatch_uid='%s_%s_riverstatefield_post' % (self.model, name))

        workflow_registry.add(self.field_name, cls)

def __getattr__(self, field_name):
        cls = self.owner if self.is_class else self.owner.__class__
        if field_name not in workflow_registry.workflows[id(cls)]:
            raise Exception("Workflow with name:%s doesn't exist for class:%s" % (field_name, cls.__name__))
        if self.is_class:
            return ClassWorkflowObject(self.owner, field_name)
        else:
            return InstanceWorkflowObject(self.owner, field_name)

def _get_workflow_class_fields(cls, model):
        from river.core.workflowregistry import workflow_registry
        return workflow_registry.workflows[id(model)]

def __init__(self, *args, **kwargs):
        super(DefaultWorkflowModelAdmin, self).__init__(*args, **kwargs)
        self.readonly_fields += tuple(workflow_registry.get_class_fields(self.model))

def all(self, cls):
        return list([getattr(self, field_name) for field_name in workflow_registry.workflows[id(cls)]])

def _get_all_workflow_classes(cls):
        from river.core.workflowregistry import workflow_registry
        return list(workflow_registry.class_index.values())