code: def update(self, entity):
          
          assert isinstance(entity, Entity), "Error: entity must have an instance of Entity"
          return self.__collection.update({'_id': entity._id}, {'$set': entity.as_dict()})
docs: Executes collection's update method based on keyword args.
  
          Example::
  
              manager = EntityManager(Product)
              p = Product()
              p.name = 'new name'
              p.description = 'new description'
              p.price = 300.0
  
              yield manager.update(p)