Help: Deleting specific DICOM tags in a nested tree with pydicom

[Eric Einspänner]

I want to delete specific DICOM tags in a DICOM file, which are contained in a nested tree and which is repeated over and over again, here is an excerpt:

(5200, 9229)  Shared Functional Groups Sequence  1 item(s) ---- 
   (0021, 0010) Private Creator                     LO: 'SIEMENS MR SDS 01'
   (0021, 10fe)  Private tag data  1 item(s) ---- 
      (0021, 0010) Private Creator                     LO: 'SIEMENS MR SDS 01'
      (0021, 1019) Private tag data                    OB: Array of 146770 elements
      (0021, 1026) Private tag data                    IS: Array of 38 elements

I've tried several approaches before, but most recently my idea was to do it via a callback function and then use walk(callback[, recursive]) from pydicom. So that I don't have this tree structure any longer I wanted to use iterall()→ Iterator[DataElement], so to say flatten the dataset.

def _private_callback(dataset, data_element):
    tags_to_remove = [
        (0x0021, 0x1019),
        (0x0021, 0x1026),
        (0x0021, 0x1171)
        ]

    for data_element in dataset.iterall():
        if data_element.tag in tags_to_remove:
            print(data_element)
            # del dataset[data_element.tag]

dcm.walk(_private_callback)

This way all tags from the tags_to_remove list will really be found. Now I want to delete them all, but as soon as I use
del dataset[data_element.tag] I get the error:

(0021, 1019) Private tag data                    OB: Array of 146770 elements
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
File ~/.conda/envs/qa_pipeline/lib/python3.9/site-packages/pydicom/tag.py:28, in tag_in_exception(tag)
     27 try:
---> 28     yield
     29 except Exception as exc:

File ~/.conda/envs/qa_pipeline/lib/python3.9/site-packages/pydicom/dataset.py:2390, in Dataset.walk(self, callback, recursive)
   2389 data_element = self[tag]
-> 2390 callback(self, data_element)  # self = this Dataset
   2391 # 'tag in self' below needed in case callback deleted
   2392 # data_element

Cell In[26], line 14, in curves_callback(dataset, data_element)
     13 print(data_element)
---> 14 del dataset[data_element.tag]

File ~/.conda/envs/qa_pipeline/lib/python3.9/site-packages/pydicom/dataset.py:636, in Dataset.__delitem__(self, key)
    635 elif isinstance(key, BaseTag):
--> 636     del self._dict[key]
    637     if self._private_blocks and key.is_private_creator:

KeyError: (0021, 1019)

The above exception was the direct cause of the following exception:
...
     30 stack_trace = traceback.format_exc()
     31 msg = f"With tag {tag} got exception: {str(exc)}\n{stack_trace}"
---> 32 raise type(exc)(msg) from exc

KeyError: 'With tag (0008, 0005) got exception: (0021, 1019)\nTraceback (most recent call last):\n  File "/home/einspaennere/.conda/envs/qa_pipeline/lib/python3.9/site-packages/pydicom/tag.py"

This is an extremely large DICOM header with about 7000 lines.