thank you for your reply. I came up with a solution. I am using composed model and so it returns the docType inside the documents in the response.

"documents": [ 
       { 
           "docType": "model-composed-1:model-doc1-en-1" 
        } 
        ..... ] 

When a doc gets extracted by this model type "model-doc1-en-1", I am expecting some content which is specifically in that particular doc type only. So when I am uploading a unknown document the content will be extracted but the expected content in that particular document will not be present and it will be filtered.