anchor.diff:  
   ## Advanced Query
   
  -Similar to multiple items:
  +Recommend items which are similar to multiple items:
   
   ```
   curl -H "Content-Type: application/json" \
  
positive.code: {"itemScores":[{"item":"i12","score":1.1700499715209998},{"item":"i21","score":1.1153550716504106},{"item":"i43","score":1.1153550716504106},{"item":"i14","score":1.0773502691896257},{"item":"i39","score":1.0773502691896257},{"item":"i26","score":1.0773502691896257},{"item":"i44","score":1.0773502691896257},{"item":"i38","score":0.9553418012614798},{"item":"i36","score":0.9106836025229592},{"item":"i46","score":0.9106836025229592}]}
  ```
  
  Only recommend items with selected categories:
  
  ```
  curl -H "Content-Type: application/json" \
  -d '{
    "items": ["i1", "i3"],
    "num": 10, "categories" : ["c4", "c3"]
  }' \
  http://localhost:8000/queries.json
  
  {"itemScores":[{"item":"i21","score":1.1153550716504106},{"item":"i14","score":1.0773502691896257},{"item":"i26","score":1.0773502691896257},{"item":"i39","score":1.0773502691896257},{"item":"i44","score":1.0773502691896257},{"item":"i45","score":0.7886751345948129},{"item":"i47","score":0.7618016810571367},{"item":"i9","score":0.7618016810571367},{"item":"i28","score":0.7618016810571367},{"item":"i6","score":0.7618016810571367}]}
  ```
  
  Only recommend items in the whiteList:
  
  ```
  curl -H "Content-Type: application/json" \
  -d '{
    "items": ["i1", "i3"],
    "num": 10, "categories" : ["c4", "c3"],
    "whiteList": ["i21", "i26", "i40"]
  }' \
  http://localhost:8000/queries.json
  
negative.code: {"itemScores":[{"item":"i21","score":1.1153550716504106},{"item":"i26","score":1.0773502691896257}]}
  ```
  
  Recommend items not in the blackList:
  
  ```
  curl -H "Content-Type: application/json" \
  -d '{
    "items": ["i1", "i3"],
    "num": 10,
    "categories" : ["c4", "c3"],
    "blackList": ["i21", "i26", "i40"]
  }' \
  http://localhost:8000/queries.json
  