chore: add interface

Author: frodehk

src/libecalc/domain/time_series_power_loss_factor.py

@@ -0,0 +1,18 @@
+from abc import ABC, abstractmethod
+
+
+class TimeSeriesPowerLossFactor(ABC):
+    """
+    Interface for evaluating power loss factor time series.
+
+    Implementations should provide methods to evaluate and return
+    power loss factor values, for each stream day.
+
+    """
+
+    @abstractmethod
+    def get_stream_day_values(self) -> list[float]:
+        """
+        Returns the evaluated power loss factor values for each stream day.
+        """
+        pass