feat: ActivationFunc classes ReLU and LeakyReLU

activations.py

@@ -0,0 +1,27 @@
+import numpy as np
+from abc import ABC, abstractmethod
+
+
+class ActivationFunc(ABC):
+    @abstractmethod
+    def derivative(v: np.ndarray) -> np.ndarray:
+        pass
+
+
+class ReLU(ActivationFunc):
+    def __call__(self, x):
+        return x * (x > 0)
+
+    def derivative(self, x):
+        return x > 0
+
+
+class LeakyReLU(ActivationFunc):
+    def __init__(self, k=0.01):
+        self.k = k
+
+    def __call__(self, x):
+        return x * (x > 0) + self.k * x * (x <= 0)
+
+    def derivative(self, x):
+        return (x > 0) + self.k * (x <= 0)