anchor.diff:                  "condition": {
                       "attributes:" [ "temperature " ],
                       "expression:" {
  -                       "q": "tempature>40"
  +                       "q": "temperature>40"
                       }
                    }
               },
  
positive.code: * Errors use a non-200 and (optionally) an error payload. See subsection on Error Responses for more detail.
  
  + Parameters
      + subId: abcdef (required, string) - subscription Id.
  
  + Request (application/json)
  
  
negative.code: 
  A `subject` contains the following subfields:
  
  * `id` or `idPattern` : Id or pattern of the affected entities (optional). Both cannot be used at the same time.
  * `type` : Type of the affected entities (optional).
  * `condition`: Condition that will trigger the notification. It can have two optional properties:
   * `attributes`: array of attribute names
   * `expression`: an expression composed of `q`, `geometry` and `coords` (see "List entities" operation above
  about this field):
  
  `id`/`idPattern` or `type` must be present.
  
  A `notification` object contains the following subfields:
  
  * `attributes`: List of attributes to be included in the notification message. If not specified (or empty), all attributes are included
    in the notification
  * `callback` : URL that will point to the service which will be invoked when a notification is generated. A NGSIv2
    compliant server must support `http` URL schema, other schemas (e.g. schemas for web sockets) could also be supported.
  * `throttling`: A period of time (in ISO8601 format) which must ellapse between two consecutive notifications. It
    is optional.
  
  Notification rules are as follow:
  
  * If `attributes` and `expression` are used, a notification is sent whenever one of the attributes in the `attributes` list changes and
    at the same time `expression` matches.
  * If `attributes` is used and `expression` is not used, a notification is sent whenever one of the attributes in the `attributes` list changes-
  * If `attributes` is not used and `expression` is used, a notification is sent whenever any of the attributes of the entity changes and
    at the same time `expression` matches.
  * If neither `attributes` or `expression` are used, a notification is sent whenever any of the attributes of the entity changes.
  
  
  ### List subscriptions [GET /v2/subscriptions]
  
  