While running tts-basics-customize-ssml.ipynb, there is an error that is thrown when calling riva_tts.synthesize(**req).

The error is the following: AttributeError: 'NoneType' object has no attribute 'items' . It refers here to the "custom_dictionary" attribute which is defined as optional.

A workaround is adding custom_dictionary={} to the request but it's not a solution.