add Optional

src/pydantic_models.py

@@ -196,7 +196,7 @@ class NationalForecastValue(ForecastValue):
         None, description="Dictionary to hold properties of the forecast, like p_levels. "
     )
 
-    expected_power_generation_normalized: float = Field(
+    expected_power_generation_normalized: Optional[float] = Field(
         None,
         ge=0,
         description="exclude the normalized power",