NotImplementedError on calling numbering_part with file that has never known bullet points

[Alexandre-SCHOEPP]

Summary

I've been having issues with adding bullet points to my .docx file (and, unlike in #204+), it is one.

I received a file using a company-made theme that does not contain any style for bullet points (among other oddities), and the was almost empty. Attempting to add bullet points programmatically (using code found on stack overflow) lead to the error below.

Adding bullet points to the file and then removing them seems to do the trick.

My question is: is there a way to add the probably missing metadata (I don't know what it is, I'm no expert in MSOffice formats) back into the file, so that my users don't have to do this ?

L;DR

Minimum viable example

import docx
doc = docx.Document('/path/to/file.docx')
doc.part.numbering_part   # error below

Stack trace

Traceback (most recent call last):
  File ".\venv\docx\parts\document.py", line 105, in numbering_part
    return cast(NumberingPart, self.part_related_by(RT.NUMBERING))
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".\venv\docx\opc\part.py", line 124, in part_related_by
    return self.rels.part_with_reltype(reltype)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".\venv\docx\opc\rel.py", line 52, in part_with_reltype
    rel = self._get_rel_of_type(reltype)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".\venv\docx\opc\rel.py", line 98, in _get_rel_of_type
    raise KeyError(tmpl % reltype)
KeyError: "no relationship of type 'http://schemas.openxmlformats.org/officeDocument/2006/relationships/numbering' in collection"

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File ".\code.py", line 3, in <module>
    value = self._fget(obj)
            ^^^^^^^^^^^^^^^
  File ".\venv\docx\parts\document.py", line 107, in numbering_part
    numbering_part = NumberingPart.new()
                     ^^^^^^^^^^^^^^^^^^^
  File ".\venv\docx\parts\numbering.py", line 14, in new
    raise NotImplementedError
NotImplementedError

• Version: 1.2.0
• Python: 3.12.12
• OS: Windows 11