code: def get(self, collection_id):
          
          url = "/collections/%s" % collection_id
          result = self._get(url)
          return CollectionModel.parse(result)
docs: Retrieve a single collection.
          To view a user’s private collections, the 'read_collections' scope is required.
  
          :param collection_id [string]: The collections’s ID. Required.
          :return: [Collection]: The Unsplash Collection.