Is there a way to add a header to a Retrofit object after it has been created ?

I create a Retrofit object using the Retrofit Builder and then at a later point need to add a certain header to it. The reason for adding it here is that this particular header needs to be added with all requests and its value is dynamic. I would like to avoid having to add this header to every network call separately. Here is how I create it:

```
    Retrofit.Builder builder = new Retrofit.Builder()
        .client(client)
        .baseUrl(String.format(baseUrl, environmentExtension) + "/")
        .addConverterFactory(GsonConverterFactory.create())
        .addCallAdapterFactory(RxJava2CallAdapterFactory.create());
builder.build();

```

I would like to add the header to this existing object.