code: function verify(postedMessage) {
  		if (
  			// Check incoming message is valid
  			typeof postedMessage === 'object' &&
  			typeof postedMessage.uuid === 'string' &&
  			postedMessage._respondable === true
  		) {
  			var messageSource = _getSource();
  			return (
  				// Check the version matches
  				postedMessage._source === messageSource ||
  				// Allow free communication with axe test
  				postedMessage._source === 'axeAPI.x.y.z' ||
  				messageSource === 'axeAPI.x.y.z'
  			);
  		}
  		return false;
  	}
docs: Verify the received message is from the "respondable" module
  @private
  @param  {Object} postedMessage The message received via postMessage
  @return {Boolean}              `true` if the message is verified from respondable