old_contents: #detection = {(1.1,-0.3):'oil', 
  
  simulated_oil = set([(1,1),(2,2),(2,3),(3,1)])
  #oil.add((1,1))
  
new_contents: #detection = {(1.1,-0.3):'oil', 
  simulated_oil = [(0,0),(0,4),(1,4),(1,2),(2,2),(2,0)]
  
  #simulated_oil = set([(1,1),(2,2),(2,3),(3,1)])
  #oil.add((1,1))
  
subject: change oil coordinates to list (-> sorted)