How can I use YDK to build service templates for NSO.

• For NSO you need to use yang to build the service templates, so maybe YDK could speed up that process.If you have a bunch of Cisco devices that are running regular IOS (3850s, ASR1ks, Cat 4510s, on IOS 15.2), not XE/XR, so NSO is the only way you can touch them with NETCONF/YANG.
• Is there any planned integration with YDK for NSO . NSO is built all in yang, so it seems like a no-brainer. NSO can create a Yang/NETCONF service template skeleton, but doing that with Python API's would make so much more sense.

Yes. YDK NSO integration is something being worked on currently. Tracked by this issue.