nbconver not working with schemdraw

I use nbconvert with different notebooks and it works.
But when I export a notebook with nbconvert in which I use schemdraw I get the following error:

...
File "/home/torsten/.local/lib/python3.10/site-packages/nbformat/validator.py", line 503, in validate
    raise error
nbformat.validator.NotebookValidationError: data.cells[{data__cells_x}] must be valid exactly by one definition (0 matches found)

Failed validating <unset> in notebook['data']['cells']:

On instance:
<unset>

My notebook:

import schemdraw
import schemdraw.elements as elm
with schemdraw.Drawing() as d:
    d+=elm.Resistor()
    d+=elm.Line().down()
    d+=elm.BatteryCell().left()
    d+=elm.Line().up()

How I use nbconvert:

jupyter nbconvert --to pdf  test.ipynb

I'm using:
Jupyternotebook 6.4.12
Python 3.10.6
on Linux Mint

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