I am currently writing the documentation of Tweetinvi for Trends and I could not find anywhere what the ParentId field mean.
Here is the json I am talking about:
"country": "Sweden",
"countryCode": "SE",
"name": "Sweden",
"parentid": 1,
"placeType": {
"code": 12,
"name": "Country"
},
"url": "http://where.yahooapis.com/v1/place/23424954",
"woeid": 23424954
},
From https://dev.twitter.com/rest/reference/get/trends/available