anchor.diff:  [cols="<,<",options="header",]
   |=======================================================================
   |Parameter |Description
  +|`k` |sets the maximum number of documents retrieved per query. This value will act in place of the usual `size` parameter 
  +in the query. Defaults to 10.
   |`normalize` | If set to `true`, this metric will calculate the https://en.wikipedia.org/wiki/Discounted_cumulative_gain#Normalized_DCG[Normalized DCG].
   |=======================================================================
   
  
positive.code: returns typical information retrieval metrics like _mean reciprocal rank_,
  _precision_ or _discounted cumulative gain_.
  
  experimental[The ranking evaluation API is new and may change in non-backwards compatible ways in the future, even on minor versions updates.]
  
  [float]
  === Overview
  
  
negative.code: <3> a list of document ratings, each entry containing the documents `_index` and `_id` together with
  the rating of the documents relevance with regards to this search request
  
  A document `rating` can be any integer value that expresses the relevance of the document on a user defined scale. For some of the metrics, just giving a binary rating (e.g. `0` for irrelevant and `1` for relevant) will be sufficient, other metrics can use a more fine grained scale.
  
  [float]
  === Template based ranking evaluation
  