3 files changed, 9 insertions, 13 deletions

diff --git a/pyecsca/sca/re/tree.py b/pyecsca/sca/re/tree.py
index 39a7ca7..6307c0f 100644
--- a/pyecsca/sca/re/tree.py
+++ b/pyecsca/sca/re/tree.py
@@ -45,7 +45,7 @@ Here we grow the trees.
 
 from math import ceil, log2
 from copy import deepcopy
-from typing import Mapping, Any, Set, List, Tuple, Optional, Dict
+from typing import Mapping, Any, Set, List, Tuple, Optional, Dict, Union
 
 import numpy as np
 import pandas as pd
@@ -548,7 +548,7 @@ class Tree:
         return tree
 
     @classmethod
-    def build(cls, cfgs: Set[Any], *maps: Map, split: str | SplitCriterion = "largest") -> "Tree":
+    def build(cls, cfgs: Set[Any], *maps: Map, split: Union[str, SplitCriterion] = "largest") -> "Tree":
         """
         Build a tree.
 
@@ -565,7 +565,7 @@ def _build_tree(
     maps: Mapping[int, Map],
     response: Optional[Any] = None,
     depth: int = 0,
-    split: str | SplitCriterion = "largest",
+    split: Union[str, SplitCriterion] = "largest",
 ) -> Node:
     pad = " " * depth
     # If there is only one remaining cfg, we do not need to continue and just return (base case 1).
diff --git a/pyecsca/sca/stacked_traces/combine.py b/pyecsca/sca/stacked_traces/combine.py
index 33bb1a6..d449d1e 100644
--- a/pyecsca/sca/stacked_traces/combine.py
+++ b/pyecsca/sca/stacked_traces/combine.py
@@ -1,5 +1,3 @@
-from __future__ import annotations
-
 from abc import ABC, abstractmethod
 
 from numba import cuda
@@ -227,9 +225,9 @@ class GPUTraceManager(BaseTraceManager):  # pragma: no cover
     @staticmethod
     def chunk_size_from_ratio(
         chunk_memory_ratio: float,
-        element_size: int | None = None,
-        item_size: int | None = None,
-        chunk_item_count: int | None = None,
+        element_size: Optional[int] = None,
+        item_size: Optional[int] = None,
+        chunk_item_count: Optional[int] = None,
     ) -> int:
         if (element_size is None) == (item_size is None and chunk_item_count is None):
             raise ValueError(
diff --git a/pyecsca/sca/stacked_traces/stacked_traces.py b/pyecsca/sca/stacked_traces/stacked_traces.py
index 476375e..3c367e9 100644
--- a/pyecsca/sca/stacked_traces/stacked_traces.py
+++ b/pyecsca/sca/stacked_traces/stacked_traces.py
@@ -1,8 +1,6 @@
-from __future__ import annotations
-
 import numpy as np
 from public import public
-from typing import Any, Mapping, Sequence
+from typing import Any, Mapping, Sequence, Optional
 
 from pyecsca.sca.trace_set.base import TraceSet
 
@@ -16,7 +14,7 @@ class StackedTraces:
 
     # TODO: Split metadata into common and per-trace
     def __init__(
-        self, samples: np.ndarray, meta: Mapping[str, Any] | None = None
+        self, samples: np.ndarray, meta: Optional[Mapping[str, Any]] = None
     ) -> None:
         if meta is None:
             meta = {}
@@ -25,7 +23,7 @@ class StackedTraces:
 
     @classmethod
     def fromarray(
-        cls, traces: Sequence[np.ndarray], meta: Mapping[str, Any] | None = None
+        cls, traces: Sequence[np.ndarray], meta: Optional[Mapping[str, Any]] = None
     ) -> "StackedTraces":
         if meta is None:
             meta = {}