code: def apply(self):
          
          raw_operations = copy.deepcopy(self.occurrences)
          for task in self.tasks:
              task(self)
          self.occurrences = raw_operations
docs: Apply the rules of the context to its occurrences.
  
          This method executes all the functions defined in
          self.tasks in the order they are listed.
  
          Every function that acts as a context task receives the
          Context object itself as its only argument.
  
          The contextualized occurrences are then stored in
          Context.contextualized.
  
          The original Occurrence instances are not modified.