anchor.diff:          },
           "properties": {
             "_id": "1",
  +          "_index": "museums",
             "name": "NEMO Science Museum",
             "price": 1750
           },
  
positive.code: `_id`::
  (string) Document `_id` for the feature's document.
  
  `<field>`::
  Field value. Only returned for fields in the `fields` parameter.
  ======
  
negative.code:         },
          "properties": {
            "_id": "4",
            "_index": "museums",
            "name": "Amsterdam Centre for Architecture",
            "price": 0
          },
  