anchor.diff:  (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`
  
positive.code: +
  .Properties of `groups`
  [%collapsible%open]
  ====
  `date_histogram`::
  (Required,
  <<search-aggregations-bucket-datehistogram-aggregation,`date_histogram`
  
negative.code: NOTE: The `avg` metric stores both the `sum` and `value_count` values. This lets
  you accurately average rollups over larger time intervals. For example, you can
  accurately roll up hourly averages into daily averages.
  =====
  
  `page_size`::
  (Optional, integer)
  