code: def get(self, *, txid, headers=None):
          
          block_list = self.transport.forward_request(
              method='GET',
              path=self.path,
              params={'transaction_id': txid},
              headers=headers,
          )
          return block_list[0] if len(block_list) else None
docs: Get the block that contains the given transaction id (``txid``)
             else return ``None``
  
          Args:
              txid (str): Transaction id.
              headers (dict): Optional headers to pass to the request.
  
          Returns:
              :obj:`list` of :obj:`int`: List of block heights.