Unexpected References Appearing in Docling OCR JSON Results

[manikrishna-m]

Hi Everyone,

I'm using Docling's basic OCR to convert a PDF into text, and I save the output as a JSON file. In one of the PDFs I'm processing, the JSON result includes a group (Group 4), which lists its children as references to texts 61 through 77. Here's a simplified snippet of what the raw JSON looks like:

{
  "children": [
    {"$ref": "#/texts/61"},
    {"$ref": "#/texts/62"},
    {"$ref": "#/texts/63"},
    {"$ref": "#/texts/64"},
    {"$ref": "#/texts/65"},
    {"$ref": "#/texts/66"},
    {"$ref": "#/texts/67"},
    {"$ref": "#/texts/68"},
    {"$ref": "#/texts/69"},
    {"$ref": "#/texts/70"},
    {"$ref": "#/texts/71"},
    {"$ref": "#/texts/72"},
    {"$ref": "#/texts/73"},
    {"$ref": "#/texts/74"},
    {"$ref": "#/texts/75"},
    {"$ref": "#/texts/76"},
    {"$ref": "#/texts/77"}
  ]
}

However, after loading this JSON using:

self.docling_doc = DoclingDocument.model_validate(doc_dict)

The children list in Group 4 unexpectedly changes. Here's what I get:

[
  RefItem(cref='#/texts/61'),
  RefItem(cref='#/texts/62'),
  RefItem(cref='#/texts/63'),
  RefItem(cref='#/texts/64'),
  RefItem(cref='#/texts/65'),
  RefItem(cref='#/texts/66'),
  RefItem(cref='#/texts/67'),
  RefItem(cref='#/texts/68'),
  RefItem(cref='#/groups/45'),  # Unexpected
  RefItem(cref='#/texts/69'),
  RefItem(cref='#/groups/44'),  # Unexpected
  RefItem(cref='#/texts/70'),
  RefItem(cref='#/texts/71'),
  RefItem(cref='#/texts/72'),
  RefItem(cref='#/texts/73'),
  RefItem(cref='#/texts/74'),
  RefItem(cref='#/texts/75')
]

As you can see, there are now references to #/groups/44 and #/groups/45, which were not present in the original JSON. Also, texts/76 and texts/77 are missing from the parsed result.

Can anyone help me understand why this is happening? Is it a parsing issue with model_validate, or could the input JSON be getting altered during validation?

Happy to provide more details if needed.

Thanks in advance!