anchor.diff:  May be specified as a single value, or as a list.
   
   `inc`::
  -Increments a numeric value by a specific amount.
  -Must be specified as a single numeric value.
  +Increments or decrements a numeric field's value by a specific amount, specified as a single integer or float.
  +Postive amounts increment the field's value, and negative decrement.
   
   === Field Storage
   
  
positive.code: * copy targets of updated fields, if any, are also non-indexed, non-stored single valued numeric docValues fields.
  
  To use in-place updates, add a modifier to the field that needs to be updated.
  The content can be updated or incrementally increased.
  
  `set`::
  Set or replace the field value(s) with the specified value(s).
  May be specified as a single value.
  
  `inc`::
  Increments a numeric value by a specific amount.
  Must be specified as a single numeric value.
  
  [TIP]
  ====
  
negative.code: ----
  {"id":"mydoc",
   "price":{"set":99},
   "popularity":{"inc":-7},
   "categories":{"add":["toys","games"]},
   "sub_categories":{"add-distinct":"under_10"},
   "promo_ids":{"remove":"a123x"},
  