if no document_id, return empty string
if no document_id, return empty string

funginstitute/patentprocessor,nikken1/patentprocessor,nikken1/patentprocessor,funginstitute/patentprocessor,yngcan/patentprocessor,nikken1/patentprocessor,funginstitute/patentprocessor,yngcan/patentprocessor,yngcan/patentprocessor