Loading multiple attachments to Document of Record via HDL

Summary:

We regularly use HDL to bulk load Document of Records with attachments, but this time we want to include multiple attachment in one Document Of Record. When I try this I get this error 

You can't supply multiple data lines for the same record in the same file because the component {BUS_OBJ_NAME} isn't date-effective.

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Content (required):

We regularly use HDL to bulk load Document of Records with attachments, but this time we want to include multiple attachment in one Document Of Record. When I try this I get this error