Checks if the given attribute name is a aggregate attribute of the given
    registered resource.

def is_domain_class_collection_attribute(ent, attr_name):
    """
    Checks if the given attribute name is a aggregate attribute of the given
    registered resource.
    """
    attr = get_domain_class_attribute(ent, attr_name)
    return attr.kind == RESOURCE_ATTRIBUTE_KINDS.COLLECTION