Changed type of LastDuplicate field to a string from a CID

network-protocols.md

@@ -61,12 +61,12 @@ type StorageDealProposal struct {
     // Duration is how long the file should be stored for
     Duration NumBlocks
 
-    // LastDuplicate is the CID of the last proposal created with identical
-    // values. This field effectively changes the CID of the current proposal,
-    // preventing collisions. This field can also be used for looking up
-    // previous proposals, however it will not be considered a reliable source
-    // for this information as data can be lost.
-    LastDuplicate Cid
+    // LastDuplicate is a string of the CID of the last proposal created with
+    // identical values. This field effectively changes the CID of the current
+    // proposal, preventing collisions. This field can also be used for looking
+    // up previous proposals, however it will not be considered a reliable
+    // source for this information as data can be lost.
+    LastDuplicate String
 
     // PaymentRef is a reference to the mechanism that the proposer
     // will use to pay the miner. It should be verifiable by the