Kentico API V8 - method CopyDocumentAttachments

Hi: I was invoked the API method InsertAsNewCultureVersion for create a new culture version of a document , but i would like to know what is the source (document, any other API method) that i have to use to configure the parameter "formGuid" when i invoke the method CopyDocumentAttachments for copying the attachments of the document to the new culture version. Because the only info that i have about the parameter in the [technical specification](https://devnet.kentico.com/docs/8_1/api/html/M_CMS_DocumentEngine_DocumentHelper_CopyDocumentAttachments.htm) is the following : formGuid
Type: OnlineSystem.Guid
Form GUID