anchor.diff:  {
       "script" : {
           "source": "ctx._source.tags.add(params.tag)",
  +        "lang": "painless",
  +        "params" : {
  +            "tag" : "blue"
  +        }
  +    }
  +}
  +--------------------------------------------------
  +// CONSOLE
  +// TEST[continued]
  +
  +We can remove a tag from the list of tags. Note that the Painless function to
  +`remove` a tag takes as its parameter the array index of the element you wish
  +to remove, so you need a bit more logic to locate it while avoiding a runtime
  +error. Note that if the tag was present more than once in the list, this will
  +remove only one occurrence of it:
  +
  +[source,js]
  +--------------------------------------------------
  +POST test/_doc/1/_update
  +{
  +    "script" : {
  +        "source": "if (ctx._source.tags.contains(params.tag)) { ctx._source.tags.remove(ctx._source.tags.indexOf(params.tag)) }",
           "lang": "painless",
           "params" : {
               "tag" : "blue"
  
positive.code:    "_index": "test",
     "_type": "_doc",
     "_id": "1",
     "_version": 6,
     "result": "noop"
  }
  --------------------------------------------------
  
negative.code: // TEST[continued]
  
  We can add a tag to the list of tags (note, if the tag exists, it
  will still add it, since it's a list):
  
  [source,js]
  --------------------------------------------------
  