split
Splits a merged document into its constituent sub-documents (page-stream segmentation) and exports the result. Every page is scored for whether it starts a new sub-document — fusing a per-page image signal with the page's text — and the contiguous page ranges are returned. The threshold and the other knobs are read from DocumentSplitSettings on the document's settings. The result is always JSON; is not consulted because only the JSON exporter serializes the split result.
Return
The exported content as a string (JSON), carrying the detected sub-document segments (1-based inclusive page ranges with their boundary confidence).