def def_attrs(cls, **kw):
    """
	Sets default attributes on a class instance

	:type cls: class
	:param cls: the class to update the given attributes in.
	:type kw: dict
	:param kw: dictionary of attributes names and values.
	"""
    for k, v in kw.items():
        if not hasattr(cls, k):
            setattr(cls, k, v)
