'Validation
@param value: the value to validate'

def __call__(self, value):

    if (not isinstance(value, (list, tuple))):
        value = [value]
    acl = 0
    for v in value:
        try:
            flag = int(v)
        except (ValueError, TypeError):
            flag = 0
        else:
            acl |= flag
    return (acl, None)
