feat: enhance indexing by adding root parameter to _DocIndex.index method

Signed-off-by: Olivier Antonelli <[email protected]>

Author: capoan

docling_core/types/doc/document.py

@@ -6221,19 +6221,31 @@ def get_item_list(self, key: str) -> list[NodeItem]:
             return getattr(self, key)
 
         def index(
-            self, doc: "DoclingDocument", page_nrs: Optional[set[int]] = None
+            self,
+            doc: "DoclingDocument",
+            page_nrs: Optional[set[int]] = None,
+            root: Optional[NodeItem] = None,
         ) -> None:
 
             orig_ref_to_new_ref: dict[str, str] = {}
-            page_delta = self._max_page - min(doc.pages.keys()) + 1 if doc.pages else 0
+
+            if root:
+                if root.parent:
+                    orig_ref_to_new_ref[root.parent.cref] = "#/body"
+                self._names.append(doc.name + root.self_ref)
+                page_delta = 0
+            else:
+                self._names.append(doc.name)
+                page_delta = (
+                    self._max_page - min(doc.pages.keys()) + 1 if doc.pages else 0
+                )
 
             if self._body is None:
                 self._body = GroupItem(**doc.body.model_dump(exclude={"children"}))
 
-            self._names.append(doc.name)
-
             # collect items in traversal order
             for item, _ in doc._iterate_items_with_stack(
+                root=root,
                 with_groups=True,
                 traverse_pictures=True,
                 included_content_layers={c for c in ContentLayer},