'The sandboxed environment will call this method to check if the
attribute of an object is safe to access.  Per default all attributes
starting with an underscore are considered private as well as the
special attributes of internal python objects as returned by the
:func:`is_internal_attribute` function.'

def is_safe_attribute(self, obj, attr, value):

    return (not (attr.startswith('_') or is_internal_attribute(obj, attr)))
