anchor.diff:  
   This engine template provides personalized recommendation for e-commerce alike applications.
   
  +The template has the following features:
  +
  +- handle out of stock items with the itemConstraint event
  +- recommend items to new user who signs up after the model is trained.
  +- recommend unseen items only.
  +
   WARNING: This template requires PredictionIO version >= 0.8.7
  +
   
   ## Usage
   
  
positive.code:     .targetEntityId(<ITEM_ID>);
  client.createEvent(viewEvent);
  
  ```
    </div>
    <div data-tab="REST API" data-lang="json">
  
negative.code: 
  Next, let's collect some training data for the app of this Engine. By default,
  the E-Commerce Recommendation Engine Template supports 2 types of entities: **user** and
  **item**, events **view** and **buy**. An item has the **categories** property, which is a list of category names (String). A user can view and buy an item.
  
  <%= partial 'shared/quickstart/install_sdk' %>
  
  The following is sample code of using different SDKs to import events of setting user and item's properties, and user-view-item events, user-buy-item event:
  
  <div class="tabs">
    <div data-tab="Python SDK" data-lang="python">
  