feat: add __str__ to CustomFixedFee and update examples/tests (#976)

Signed-off-by: undefinedIsMyLife <shinetina169@gmail.com>

Author: undefinedIsMyLife

CHANGELOG.md

@@ -7,6 +7,7 @@ This changelog is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.
 ## [Unreleased]
 
 ### Added
+- Added __str__() to CustomFixedFee and updated examples and tests accordingly.
 - Added a github template for good first issues
 - Added `.github/workflows/bot-assignment-check.yml` to limit non-maintainers to 2 concurrent issue assignments.
 - Added all missing fields to __str__() method and updated `test_tokem_info.py`

README.md

@@ -134,4 +134,4 @@ This project is licensed under the [Apache License 2.0](LICENSE).
 
 ---
 
-**Latest release:** Check [PyPI](https://pypi.org/project/hiero-sdk-python/) or [GitHub Releases](https://github.com/hiero-ledger/hiero-sdk-python/releases)
+**Latest release:** Check [PyPI](https://pypi.org/project/hiero-sdk-python/) or [GitHub Releases](https://github.com/hiero-ledger/hiero-sdk-python/releases)

examples/tokens/custom_fixed_fee.py

@@ -14,11 +14,9 @@ def custom_fixed_fee():
         fee_collector_account_id=AccountId(0, 0, 456),
         all_collectors_are_exempt=False,
     )
-    print("CustomFixedFee:")
-    print(f"Amount: {fixed_fee.amount}")
-    print(f"Denominating Token ID: {fixed_fee.denominating_token_id}")
-    print(f"Fee Collector Account ID: {fixed_fee.fee_collector_account_id}")
-    print(f"All Collectors Exempt: {fixed_fee.all_collectors_are_exempt}")
+    print("\n--- Custom Fixed Fee ---")
+    print(fixed_fee)
+
     # Convert to protobuf
     fixed_fee_proto = fixed_fee._to_proto()
 

src/hiero_sdk_python/tokens/custom_fixed_fee.py

@@ -61,6 +61,30 @@ def __init__(
         super().__init__(fee_collector_account_id, all_collectors_are_exempt)
         self.amount = amount
         self.denominating_token_id = denominating_token_id
+        
+    def __str__(self) -> str:
+        """Return a user-friendly string representation of the CustomFixedFee.
+
+        Displays all fields in insertion order with aligned formatting.
+        TokenId and AccountId objects are displayed in Hedera notation (e.g., 0.0.123).
+        """
+
+        fields = {
+            key.replace("_", " ").title(): value
+            for key, value in self.__dict__.items()
+        }
+
+        if not fields:
+            return f"{self.__class__.__name__}()"
+
+        max_len = max(len(name) for name in fields)
+
+        lines = [f"{self.__class__.__name__}:"]
+        for name, value in fields.items():  # preserves insertion order
+            lines.append(f"    {name:<{max_len}} = {value}")  # uses __str__()
+
+        return "\n".join(lines)
+
 
     def set_amount_in_tinybars(self, amount: int) -> "CustomFixedFee":
         """Sets the fee amount in tinybars.

tests/unit/test_custom_fee.py

@@ -9,23 +9,60 @@
 
 pytestmark = pytest.mark.unit
 
-def test_custom_fixed_fee():
+def test_custom_fixed_fee_proto_round_trip():
+    """Ensure CustomFixedFee protobuf serialization and deserialization behave correctly."""
     fee = CustomFixedFee(
         amount=100,
         denominating_token_id=TokenId(0, 0, 123),
         fee_collector_account_id=AccountId(0, 0, 456),
         all_collectors_are_exempt=True,
     )
 
-    proto = fee._to_proto()  # Changed from _to_protobuf
-    new_fee = CustomFixedFee._from_proto(proto)  # Changed from CustomFee._from_protobuf
+    proto = fee._to_proto()
+    new_fee = CustomFixedFee._from_proto(proto)
 
     assert isinstance(new_fee, CustomFixedFee)
     assert new_fee.amount == 100
     assert new_fee.denominating_token_id == TokenId(0, 0, 123)
     assert new_fee.fee_collector_account_id == AccountId(0, 0, 456)
     assert new_fee.all_collectors_are_exempt is True
 
+def test_custom_fixed_fee_str():
+    """Test the string representation of CustomFixedFee."""
+    fee = CustomFixedFee(
+        amount=100,
+        denominating_token_id=TokenId(0, 0, 123),
+        fee_collector_account_id=AccountId(0, 0, 456),
+        all_collectors_are_exempt=False,
+    )
+
+    fee_str = fee.__str__()
+
+    # Basic checks
+    assert "CustomFixedFee" in fee_str
+    assert "Amount" in fee_str
+    assert "Denominating Token Id" in fee_str
+    assert "Fee Collector Account Id" in fee_str
+    assert "All Collectors Are Exempt" in fee_str
+
+    # Key-value extraction
+    kv = {}
+    for ln in fee_str.splitlines()[1:]:
+        if "=" in ln:
+            key, val = ln.split("=", 1)
+            kv[key.strip()] = val.strip()
+
+    expected = {
+        "Amount": "100",
+        "Denominating Token Id": "0.0.123",
+        "Fee Collector Account Id": "0.0.456",
+        "All Collectors Are Exempt": "False",
+    }
+
+    for key, val in expected.items():
+        assert kv[key] == val, f"{key} incorrect in string representation"
+
+
 def test_custom_fractional_fee_str():
     """Test the string representation of CustomFractionalFee."""
     fee = CustomFractionalFee(