anchor.diff:  +
   .Properties of `histogram`
   [%collapsible%open]
  -=====
  +======
   `fields`::
   (Required*, array of strings)
   Array of <<number,numeric>> fields to group. If you specify a `histogram`
  
positive.code: (Required*, integer)
  Numeric interval used to group the `fields`. If you specify a `histogram`
  object, this property is required.
  =====
  
  `terms`::
  (Optional, <<search-aggregations-bucket-terms-aggregation,`terms`
  
negative.code: +
  .Properties of `metrics` objects
  [%collapsible%open]
  =====
  `field`::
  (Required*, string)
  <<number,Numeric>> field to collect metrics for. If you specify a `metrics`
  