unable to set "setPersistenceCacheSizeBytes"

Hi, I'm unable to use the "setPersistenceCacheSizeBytes" for local storage.
As stated in the docs it should apply to Database default instance:
https://firebase.google.com/docs/reference/android/com/google/firebase/database/FirebaseDatabase#public-synchronized-void-setpersistencecachesizebytes-long-cachesizeinbytes

I'm trying with :
FirebaseDatabase.DefaultInstance.setPersistenceCacheSizeBytes(10000000);

But Unity tells me:
'FirebaseDatabase' does not contain a definition for 'setPersistenceCacheSizeBytes' and no accessible extension method 'setPersistenceCacheSizeBytes' accepting a first argument of type 'FirebaseDatabase' could be found (are you missing a using directive or an assembly reference?)

Is there another way to set it ?

Can you help me out ?

Thanks in advance.

Unity editor version: Unity 2019.2.12f1
Firebase Unity SDK version: 6.70
Firebase plugins in use: DATABASE
Platform you are using the Unity editor on : WINDOWS 10
Platform you are targeting: Android
Scripting Runtime: MONO Net 4x