code: def addto_collection(self, collection, payload):
          
          ident = payload["key"]
          modified = payload["version"]
          # add the collection data from the item
          modified_collections = payload["data"]["collections"] + [collection]
          headers = {"If-Unmodified-Since-Version": str(modified)}
          headers.update(self.default_headers())
          req = requests.patch(
              url=self.endpoint
              + "/{t}/{u}/items/{i}".format(
                  t=self.library_type, u=self.library_id, i=ident
              ),
              data=json.dumps({"collections": modified_collections}),
              headers=headers,
          )
          self.request = req
          try:
              req.raise_for_status()
          except requests.exceptions.HTTPError:
              error_handler(req)
          return True
docs: Add one or more items to a collection
          Accepts two arguments:
          The collection ID, and an item dict