diff --git a/pytm/flows.py b/pytm/flows.py
index b05c0ca..9ef3d85 100644
--- a/pytm/flows.py
+++ b/pytm/flows.py
@@ -2,7 +2,7 @@
 from pytm import Element
 
 
-def req_reply(src: Element, dest: Element, req_name: str, reply_name=None) -> (DF, DF):
+def req_reply(src: Element, dest: Element, req_name: str, reply_name=None) -> tuple[DF, DF]:
     """
     This function creates two datflows where one dataflow is a request
     and the second dataflow is the corresponding reply to the newly created request.
@@ -31,7 +31,7 @@ def req_reply(src: Element, dest: Element, req_name: str, reply_name=None) -> (D
     return req, reply
 
 
-def reply(req: DF, **kwargs) -> DF:
+def reply(req: DF, **kwargs) -> tuple[DF, DF]:
     """
     This function takes a dataflow as an argument and returns a new dataflow, which is a response to the given dataflow.
 
diff --git a/pytm/pytm.py b/pytm/pytm.py
index d710c8c..0b08080 100644
--- a/pytm/pytm.py
+++ b/pytm/pytm.py
@@ -9,7 +9,7 @@
 from typing import ClassVar
 
 from pydantic import ValidationError
-from pydantic.fields import PydanticUndefined
+from pydantic_core import PydanticUndefined
 
 from collections import defaultdict
 from collections.abc import Iterable, Mapping
diff --git a/pytm/template_engine.py b/pytm/template_engine.py
index 172d152..da2c6d6 100644
--- a/pytm/template_engine.py
+++ b/pytm/template_engine.py
@@ -14,25 +14,25 @@ class SuperFormatter(string.Formatter):
     """Lightweight formatter with helpers for reports and templates."""
 
     def format_field(
-        self, value: Any, spec: str
+        self, value: Any, format_spec: str
     ) -> Any:  # noqa: D401 - same semantics as base
-        if not spec:
-            return super().format_field(value, spec)
+        if not format_spec:
+            return super().format_field(value, format_spec)
 
-        if spec.startswith("repeat"):
-            return self._format_repeat(value, spec)
+        if format_spec.startswith("repeat"):
+            return self._format_repeat(value, format_spec)
 
-        if spec.startswith("call:"):
-            return self._format_call(value, spec)
+        if format_spec.startswith("call:"):
+            return self._format_call(value, format_spec)
 
-        if spec.startswith("if") or spec.startswith("not"):
-            return self._format_conditional(value, spec)
+        if format_spec.startswith("if") or format_spec.startswith("not"):
+            return self._format_conditional(value, format_spec)
 
-        return super().format_field(value, spec)
+        return super().format_field(value, format_spec)
 
-    def _format_repeat(self, value: Any, spec: str) -> str:
+    def _format_repeat(self, value: Any, format_spec: str) -> str:
         """Handle the custom repeat operator."""
-        template = spec.partition(":")[2]
+        template = format_spec.partition(":")[2]
         if isinstance(value, dict):
             iterable: Iterable[Any] = value.items()
         elif isinstance(value, Iterable) and not isinstance(value, (str, bytes)):
@@ -41,9 +41,9 @@ def _format_repeat(self, value: Any, spec: str) -> str:
             iterable = []
         return "".join(self.format(template, item=item) for item in iterable)
 
-    def _format_call(self, value: Any, spec: str) -> Any:
+    def _format_call(self, value: Any, format_spec: str) -> Any:
         """Evaluate callable values or report utility helpers."""
-        _, _, remainder = spec.partition(":")
+        _, _, remainder = format_spec.partition(":")
 
         if callable(value):
             result = value()
@@ -56,11 +56,11 @@ def _format_call(self, value: Any, spec: str) -> Any:
             return "".join(self.format(template, item=item) for item in result)
         return result
 
-    def _format_conditional(self, value: Any, spec: str) -> str:
+    def _format_conditional(self, value: Any, format_spec: str) -> str:
         """Render content conditionally based on truthiness of *value*."""
-        _, _, template = spec.partition(":")
+        _, _, template = format_spec.partition(":")
         result = value() if callable(value) else value
-        if spec.startswith("if"):
+        if format_spec.startswith("if"):
             return template if result else ""
         return template if not result else ""
 
diff --git a/pytm/tm.py b/pytm/tm.py
index fb75e0c..703bad8 100644
--- a/pytm/tm.py
+++ b/pytm/tm.py
@@ -105,6 +105,7 @@ class TM(BaseModel, metaclass=TMModelMetaclass):
 
     _state: ClassVar[TMState] = TMState()
     _state_attributes: ClassVar[Dict[str, _StateAttribute]] = {}
+    _duplicate_ignored_attrs: ClassVar[tuple[str, ...]] = ()
 
     @classmethod
     def _register_state_attribute(cls, name: str, descriptor: _StateAttribute) -> None: