chore: add getter by address and nonce to TransactionPool (#402)

crates/mempool/src/transaction_pool.rs

@@ -59,9 +59,17 @@ impl TransactionPool {
         Ok(tx)
     }
 
-    pub fn get(&self, tx_hash: TransactionHash) -> MempoolResult<&ThinTransaction> {
+    pub fn get_by_tx_hash(&self, tx_hash: TransactionHash) -> MempoolResult<&ThinTransaction> {
         self.tx_pool.get(&tx_hash).ok_or(MempoolError::TransactionNotFound { tx_hash })
     }
+
+    pub fn get_by_address_and_nonce(
+        &self,
+        address: ContractAddress,
+        nonce: Nonce,
+    ) -> Option<&TransactionReference> {
+        self.txs_by_account.get(address, nonce)
+    }
 }
 
 #[derive(Debug, Default)]
@@ -85,4 +93,8 @@ impl AccountTransactionIndex {
 
         removed_tx
     }
+
+    pub fn get(&self, address: ContractAddress, nonce: Nonce) -> Option<&TransactionReference> {
+        self.0.get(&address)?.get(&nonce)
+    }
 }