Update optimize.py

Author: rolfjl

popt/loop/optimize.py

@@ -3,13 +3,14 @@
 import numpy as np
 import time
 import pickle
+from abc import ABC, abstractmethod
 
 # Internal imports
 import popt.misc_tools.optim_tools as ot
 from ensemble.logger import PetLogger
 
 
-class Optimize:
+class Optimize(ABC):
     """
     Class for ensemble optimization algorithms. These are classified by calculating the sensitivity or gradient using
     ensemble instead of classical derivatives. The loop is else as a classic optimization loop: a state (or control