anchor.diff:          },
           "properties": {
             "_id": "3",
  +          "_index": "museums",
             "name": "Nederlands Scheepvaartmuseum",
             "price": 1650
           },
  
positive.code:         },
          "properties": {
            "_id": "1",
            "name": "NEMO Science Museum",
            "price": 1750
          },
  
negative.code: `_id`::
  (string) Document `_id` for the feature's document.
  
  `_index`::
  (string) Name of the index for the feature's document.
  
  `<field>`::
  Field value. Only returned for fields in the `fields` parameter.
  ======
  