'Safely get the underlying attribute definition as a Validator.
Args:
key: Name of attribute to get.
Returns:
Validator associated with key or attribute value wrapped in a
validator.'

@classmethod
def GetValidator(self, key):

    if (key not in self.ATTRIBUTES):
        raise ValidationError(("Unexpected    attribute    '%s'    for    object    of    type    %s." % (key, self.__name__)))
    return AsValidator(self.ATTRIBUTES[key])
