conflicting transactions

lib/transaction.py

@@ -797,6 +797,14 @@ class Transaction:
     def serialize_outpoint(self, txin):
         return bh2u(bfh(txin['prevout_hash'])[::-1]) + int_to_hex(txin['prevout_n'], 4)
 
+    @classmethod
+    def get_outpoint_from_txin(cls, txin):
+        if txin['type'] == 'coinbase':
+            return None
+        prevout_hash = txin['prevout_hash']
+        prevout_n = txin['prevout_n']
+        return prevout_hash + ':%d' % prevout_n
+
     @classmethod
     def serialize_input(self, txin, script):
         # Prev hash and index