How to reference original value of contract attachments using Groovy?

Summary:

We are trying to create groovy script for Contracts that would check if a field changed an attribute and we are using 'getOriginalAttributeValue' to reference the original value. It is working fine for most fields except attachments wherein we will receive a message that 'Non-entity/Non-scalar attributes are not versioned'.
Is there a way to reference the original value of attachments/contract documents?

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):

def prevDoc=getOriginalAttributeValue('AiGenerateSummaryDocs')
def currDoc='AiGenerateSummaryDocs'