Implement ReLU layer

src/layer.py

@@ -32,7 +32,7 @@ class Layer(ABC):
         pass
 
     @abstractmethod
-    def d_output_wrt_inputs(self) -> np.ndarray:
+    def d_output_wrt_inputs(self, x: np.ndarray) -> np.ndarray:
         pass
 
 
@@ -64,5 +64,24 @@ class Dense(Layer):
         """
         return (inputs, np.array([1]))
 
-    def d_output_wrt_inputs(self) -> np.ndarray:
+    def d_output_wrt_inputs(self, x: np.ndarray) -> np.ndarray:
         return self.__w
+
+
+class ReLU(Layer):
+    def forward(self, x: np.ndarray) -> np.ndarray:
+        return (x > 0) * x
+
+    @property
+    def parameters(self) -> tuple[np.ndarray, ...]:
+        return ()
+
+    @parameters.setter
+    def parameters(self, parameters: tuple[np.ndarray, ...]) -> None:
+        return
+
+    def d_output_wrt_parameters(self, inputs: np.ndarray) -> tuple[np.ndarray, ...]:
+        return ()
+
+    def d_output_wrt_inputs(self, x: np.ndarray) -> np.ndarray:
+        return (x > 0) * 1.0