code: def References(self):
          
          if self.__references is None:
  
              refs = {}
  
              # group by the input prevhash
              for hash, group in groupby(self.inputs, lambda x: x.PrevHash):
  
                  tx, height = GetBlockchain().GetTransaction(hash.ToBytes())
                  if tx is not None:
                      for input in group:
                          refs[input] = tx.outputs[input.PrevIndex]
  
              self.__references = refs
  
          return self.__references
docs: Get all references.
  
          Returns:
              dict:
                  Key (UInt256): input PrevHash
                  Value (TransactionOutput): object.