anchor.diff:  + Parameters
       + entityId: Bcn_Welt (required, string) - Entity ID
       + attrName: temperature (required, string) - Attribute to be retrieved.
  -    + options: (optional, string) - Options dictionary
   
   + Response 200 (application/json)
   
  
positive.code: 
  # Group Attribute Value
  
  ## By Entity ID [/v2/entities/{entityId}/attrs/{attrName}/value{?options}]
  
  ### Get attribute data [GET /v2/entities/{entityId}/attrs/{attrName}/value{?options}]
  
  It returns a JSON object with a `value` propierty with the value of the attribute. The `text` option
  indicates that the attribute value must be provided as plain text (text/plain).
  
  Response:
  
  
negative.code: 
  ### Update attribute value [PUT /v2/entities/{entityId}/attrs/{attrName}/value]
  
  The request payload is the new attribute value.
  
  * If the request payload MIME type is `application/json`, then the value of the attribute is set to the JSON object or array
    coded in the payload (if the payload is not a valid JSON document, then an error is returned).
  * If the request payload MIME type is `text/plain`, then the following algorithm is applied to the payload:
    * If the payload starts and ends with citation-marks (`"`), the value is taken as a string (the citation marks themselves are not
      considered part of the string)
    * If `true` or `false`, the value is taken as a boolean.
    * If `null`, the value is taken as null.
    * If these first three tests 'fail', the text is interpreted as a number.
    * If not a number, then an error is returned and the attribute's value is unchanged.
  
  The payload MIME type in request is specified in the `Content-Type` HTTP header.
  
  Response:
  
  