interpolation of missing data in pandas before passing to draco2

there are missing data in between years, plot is confusing.

<img width="496" height="459" alt="Image" src="https://github.com/user-attachments/assets/46666e69-3360-48fc-9a73-bbf813dfe6f9" />

data:

<img width="626" height="489" alt="Image" src="https://github.com/user-attachments/assets/787d21e3-1c31-4738-9fd3-20e3fe36fef9" />