code: public InstagramSubscription verifyToken(String verifyToken) {
  		Preconditions.checkEmptyString(verifyToken, "Invalid 'verifyToken' key");
  
  		this.params.put(Constants.VERIFY_TOKEN, verifyToken);
  
  		return this;
  	}
docs: Configure the verifyToken for the subscription
  
  @param verifyToken The token for the subscription
  @return the {@link InstagramSubscription} instance for method chaining