Converts N input documents to 1 output file, Input document will be retrieved using
A2WDocumentReader callback implementation by passing in the document id given as parameter
to this API, A2WDocumentReader's "read" function is called for each input document id.
Converts N input documents to 1 output buffer, Input document will be retrieved using
A2WDocumentReader callback implementation by passing in the document id given as parameter
to this API, A2WDocumentReader's "read" function is called for each input document id.