anchor.diff:      "my_script_field": {
         "script": {
           "lang": "painless",
  -        "inline": "doc['some_field'].value.toLowerCase()" <1>
  +        "source": "doc['some_field'].value.toLowerCase()" <1>
         }
       }
     }
  
positive.code:     "my_script_field": {
        "script": {
          "lang": "painless",
          "inline": "doc['some_field'].value + '_' + doc['another_field'].value" <2>
        }
      }
    }
  
negative.code:     "total_error_count": { <2>
        "script": {
          "lang": "expression",
          "source": "doc['error_count'].value + doc['aborted_count'].value"
        }
      }
    }
  