How to calculate billing characters of Vertex AI in offline mode, without using the FREE Post API?

Question

I am trying to calculate the number (and if possible the exact list) of billable Vertex AI characters of a text.

Apart from the FREE API here, is there a way to implement locally the method to calculate those billing characters ?

For instance with chatGPT and tiktoken here, you can do it offline.

The advantages is that I would have :

• no need internet connection
• no limitation of parallel calls
• exact list of billable characters

Thank you in advance !

Cheers,