docs: def create_budget(self, wallet_name, model_uuid, limit):
          """Create a new budget for a model and wallet.
  
          @param the name of the wallet.
          @param the model UUID.
          @param the new value of the limit.
          @return a success string from the plans server.
          @raise ServerError via make_request.
          """
          request = {
              'model': model_uuid,
              'limit': limit,
          }
          return make_request(
              '{}wallet/{}/budget'.format(self.url, wallet_name),
              method='POST',
              body=request,
              timeout=self.timeout,
              client=self._client)