Check existnce of item based on get collection call.

        :param collection: container object -- capable of get_collection()
        :param item_name: str -- name of item to search for in collection

def _check_existence_by_collection(self, container, item_name):
        '''Check existnce of item based on get collection call.

        :param collection: container object -- capable of get_collection()
        :param item_name: str -- name of item to search for in collection
        '''

        coll = container.get_collection()
        for item in coll:
            if item.name == item_name:
                return True
        return False