MAINT: Extend base model to include Image - only preparation for othe…

…r models to come

src/darsia/signals/models/basemodel.py

@@ -6,16 +6,25 @@
 
 import abc
 import copy
-from typing import Literal, Optional, Union
+from typing import Literal, Optional, Union, overload
 
 import numpy as np
 
 import darsia
 
 
 class Model:
+
+    @abc.abstractmethod
+    @overload
+    def __call__(self, signal: np.ndarray) -> np.ndarray: ...
+
+    @abc.abstractmethod
+    @overload
+    def __call__(self, signal: darsia.Image) -> darsia.Image: ...
+
     @abc.abstractmethod
-    def __call__(self, img: np.ndarray) -> np.ndarray:
+    def __call__(self, img: np.ndarray | darsia.Image) -> np.ndarray | darsia.Image:
         """
         Translation of signal to data.
         """