feat: added method to get signable_node tx_body_bytes

Signed-off-by: Manish Dait <daitmanish88@gmail.com>

Author: manishdait

src/hiero_sdk_python/transaction/transaction.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import hashlib
+from dataclasses import dataclass
 from typing import TYPE_CHECKING, Literal, overload
 
 from hiero_sdk_python.account.account_id import AccountId
@@ -1142,3 +1143,34 @@ def high_volume(self) -> bool:
             bool: True if high-volume throttles are enabled.
         """
         return self._high_volume
+
+    def get_signable_node_body_bytes_list(self) -> list[SignableNodeTransactionBodyBytes]:
+        """Returns a list of SignableNodeTransactionBodyBytes objects."""
+        self._require_frozen()
+
+        signable_node_transaction_body_bytes: list[SignableNodeTransactionBodyBytes] = []
+
+        for node_transaction_bodies in self._transaction_body_bytes.values():
+            for transaction_bytes in node_transaction_bodies.values():
+                try:
+                    transaction_body = transaction_pb2.TransactionBody()
+                    transaction_body.ParseFromString(transaction_bytes)
+                except Exception as e:
+                    raise ValueError(f"Failed to parse transaction bytes: {e}") from e
+
+                signable_node_transaction_body_bytes.append(
+                    SignableNodeTransactionBodyBytes(
+                        node_id=AccountId._from_proto(transaction_body.nodeAccountID),
+                        transaction_id=TransactionId._from_proto(transaction_body.transactionID),
+                        transaction_bytes=transaction_body.SerializeToString(),
+                    )
+                )
+
+        return signable_node_transaction_body_bytes
+
+
+@dataclass
+class SignableNodeTransactionBodyBytes:
+    node_id: AccountId | None = None
+    transaction_id: TransactionId | None = None
+    transaction_bytes: bytes | None = None

tests/unit/transaction_test.py

@@ -25,7 +25,7 @@
 from hiero_sdk_python.response_code import ResponseCode
 from hiero_sdk_python.tokens.token_id import TokenId
 from hiero_sdk_python.tokens.token_mint_transaction import TokenMintTransaction
-from hiero_sdk_python.transaction.transaction import Transaction
+from hiero_sdk_python.transaction.transaction import SignableNodeTransactionBodyBytes, Transaction
 from hiero_sdk_python.transaction.transaction_id import TransactionId
 from hiero_sdk_python.transaction.transaction_receipt import TransactionReceipt
 from hiero_sdk_python.transaction.transaction_response import TransactionResponse
@@ -730,3 +730,47 @@ def test_serialization_of_single_transaction():
     assert tx1.initial_balance == tx2.initial_balance
     assert tx2.node_account_id == node_account_id
     assert tx2.transaction_id == transaction_id
+
+
+def test_get_signable_node_bytes():
+    """Test that get signable node body bytes return the transaction body bytes lists."""
+    key = PrivateKey.generate_ecdsa()
+    transaction_id = TransactionId.generate(AccountId(0, 0, 5))
+    node_account_ids = [AccountId(0, 0, 4), AccountId(0, 0, 3)]
+
+    tx = (
+        AccountCreateTransaction()
+        .set_key_without_alias(key)
+        .set_initial_balance(1)
+        .set_account_memo("test account")
+        .set_node_account_ids(node_account_ids)
+        .set_transaction_id(transaction_id)
+        .freeze()
+    )
+
+    signable_bytes = tx.get_signable_node_body_bytes_list()
+
+    assert signable_bytes is not None
+    assert isinstance(signable_bytes, list)
+    assert len(signable_bytes) == 2  # single tx_id for 2 node_ids
+    for tx_bytes in signable_bytes:
+        assert isinstance(tx_bytes, SignableNodeTransactionBodyBytes)
+
+
+def test_get_signable_node_bytes_raise_error_if_not_frozen():
+    """Test that get signable node body bytes rraise exception if the transaction not frozen."""
+    key = PrivateKey.generate_ecdsa()
+    transaction_id = TransactionId.generate(AccountId(0, 0, 5))
+    node_account_ids = [AccountId(0, 0, 4), AccountId(0, 0, 3)]
+
+    tx = (
+        AccountCreateTransaction()
+        .set_key_without_alias(key)
+        .set_initial_balance(1)
+        .set_account_memo("test account")
+        .set_node_account_ids(node_account_ids)
+        .set_transaction_id(transaction_id)
+    )
+
+    with pytest.raises(Exception, match="Transaction is not frozen"):
+        tx.get_signable_node_body_bytes_list()