Update brain to be an abstract class

brain/brain.py

+from abc import ABC, abstractmethod
 from model.object_type import ObjectType
 from model.cup_object import CupObject
 from pygame.math import Vector2
 
-class Brain():
+class Brain(ABC):
 
     def __init__(self, side):
         self.side = side
@@ -34,5 +35,6 @@ class Brain():
         objects.sort(key = lambda agent: self.pos.distance_to(agent.pos))
         return objects
 
+    @abstractmethod
     def action(self):
-        raise Exception('action() have not been setup')
+        raise Exception('action() has not been setup')