'Validates a value as a proper credentials object.
Args:
value: A value to be set on the property.
Raises:
TypeError if the value is not an instance of Credentials.'

def _validate(self, value):

    _LOGGER.info('validate:    Got    type    %s', type(value))
    if ((value is not None) and (not isinstance(value, client.Credentials))):
        raise TypeError('Property    {0}    must    be    convertible    to    a    credentials    instance;    received:    {1}.'.format(self._name, value))
