fluent-json-schema with transforms in fastify schema validation

Question

I am using fluent-json-schema for input validation. However I was wondering whether we can have custom function/hook before doing certain validations. For example let's take a very simple json such as;

`
   {
       "loginid:"",
       "password":""
   }
`

In this case additionally to the provided validation methods I would like to;

1. Trim() the data so that whitespaces are removed. May be I can have a custom transform as in here (is it possible in fluent-json-schema library)?

2. Then validate for empty string ("") as well.

Is there a way to do this using fluent-json-schema