microservice architecure : a layer between service and its client

I'm quite a newbie to microservices architecture. I'm referring to one of my clients projects with microservice architecture. It has one of the service as Notification

Order ->(talks to)-> Notification client(as a lib) -> calls api from - > Notification service.

I don't really understand the purpose of having a client in between, where in it has a few exceptions handled for hitting the api. I understand, microservices communicate via api gateway but I feel Notification Client is just an addon. I tried to figure out the terminology used for this kind of implementation but in vain.

Please help me understand this use case.

Solution

It may feel that the client is redundant if Order service is the only microservice that is consuming the APIs. But considering the notification service is getting used by a few more microservices having a notification client as a lib makes sense. The reason is,

The client lib will wrap all the API calls and their implementation so that other services can simply call it just like a method.
Other services don't have to write REST client for notification service when it wants to make use of the APIs.
Same client lib can be shared by other microservices without actually writing code to call the APIs.
Any changes/fixes made to the notification service can be cascaded to other services by simply changing the version of the client lib.