Tensorflow.python.framework.errors_impl.notfounderror: Op type not registered 'NonMaxSuppressionV3'

Hello Community,
My former collegue trained a TF algoritme and I am running his script and I face the following error:
'tensorflow.python.framework.errors_impl.notfounderror: Op type not registered ‘NonMaxSuppressionV3’

Can anybody help me out with this?

with kind regards,
Tim

Can you share the code?