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