nan.document.basic nan.document True True pending write({'state':'pending'}) scanning scan_document_background() write({'state':'scanning'}) function scanned scan_document() write({'state':'scanned'}) function verified write({'state':'verified'}) function processing process_document_background() write({'state':'processing'}) function True processed process_document() write({'state':'processed'}) function scan_document verify_document process_document pending_to_scanning scanning_to_scanned verified_to_processing processing_to_processed scanned_to_pending verified_to_scanned