old_contents: from synergine.core.exceptions import NotConcernedEvent
  from synergine.core.simulation.mechanism.Mechanism import Mechanism
  
  
  class Event():
  
      concern = None
      _each_cycle = 1
  
      def __init__(self, actions):
          self._actions = actions
          self._mechanism = Mechanism
  
      def get_mechanism_class(self):
          return self._mechanism
  
      @classmethod
      def get_each_cycle(cls):
          return cls._each_cycle
  
      def observe(self, object_id, context, parameters={}):
          active_actions = []
          try:
              parameters = self._prepare(object_id, context, parameters)
              for action in self._actions:
                  action_object = action(object_id, parameters)
                  action_object.prepare(context)
                  active_actions.append(action_object)
          except NotConcernedEvent:
              pass  # Object not concerned by this event
  
          return active_actions
  
      def _prepare(self, object_id, context, parameters={}):
          return parameters
new_contents: from synergine.core.exceptions import NotConcernedEvent
  from synergine.core.simulation.mechanism.Mechanism import Mechanism
  
  
  class Event():
  
      concern = None
      _each_cycle = 1
  
      def __init__(self, actions):
          self._actions = actions
          self._mechanism = Mechanism
  
      def get_mechanism_class(self):
          return self._mechanism
  
      @classmethod
      def get_each_cycle(cls):
          return cls._each_cycle
  
      def observe(self, object_id, context, parameters={}):
          active_actions = []
          try:
              parameters = self._prepare(object_id, context, parameters)
              for action in self._actions:
                  action_object = action(object_id, parameters)
                  action_object.prepare(context)
                  active_actions.append(action_object)
          except NotConcernedEvent:
              pass  # Object not concerned by this event
  
          return active_actions
  
      def _prepare(self, object_id, context, parameters={}):
          raise NotImplementedError()
subject: Revert "Event::_prepare return parameters by default"