How to access supporting document object through groovy script

Summary:

Hello

I need to implement a process where i need to check if the creator has added certain mandatory document in supporting documents section under contracts.

I tried access the SupportingDocument object through groovy but in vain.

Below is what i tried :

For testing purposes : Under trigger- i tried calling the Supporting documents object as , SupportingDocs.Count() , but it always shows 0.

Ay other thoughts how i can check If supporting docs are present or not for a contract besides webservice(internal REST) call ?

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