Special-case codegen for 'CreateStreamOut'

This works around a bug with the generated openapi code - some of
the generated code expects it to be a class (with a `from_dict` method)

python/templates/model.py.jinja

@@ -1,5 +1,6 @@
 {% set class_name = model.class_info.name %}
-{% if model.required_properties == [] and model.optional_properties == [] %}
+# TODO - remove this special case when we fix the generated code for empty openapi structs
+{% if model.required_properties == [] and model.optional_properties == [] and model.class_info.name != "CreateStreamOut"  %}
 from typing import Any, Dict, Type, TypeVar
 
 T = TypeVar("T", bound="{{ class_name }}")