code: def index_of(self, name):
          
          result = -1
          for index, actor in enumerate(self.actors):
              if actor.name == name:
                  result = index
                  break
          return result
docs: Returns the index of the actor with the given name.
  
          :param name: the name of the Actor to find
          :type name: str
          :return: the index, -1 if not found
          :rtype: int