def get_instance_type(entity_name, instance_dict=None):
    """
    :param entity_name: name of an entity;
    :param instance_dict: dictionary that contains the instance type of each entity;
    :return: the instance type of the provided entity;
    
    Get the instance type of a given entity, as specified by the instance_dict;
    If the entity is not present, return "owl#Thing";
    """
    if (instance_dict is None) or (entity_name not in instance_dict):
        return "owl#Thing"
    else:
        return instance_dict[entity_name]