fix python type hints

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "perpetual"
-version = "0.3.1"
+version = "0.3.2"
 edition = "2021"
 authors = ["Mutlu Simsek <msimsek@perpetual-ml.com>"]
 homepage = "https://perpetual-ml.com"

README.md

@@ -63,7 +63,7 @@ pip install perpetual
 To use in a Rust project, add the following to your Cargo.toml file to get the package from [crates.io](https://crates.io/crates/perpetual).
 
 ```toml
-perpetual = "0.3.1"
+perpetual = "0.3.2"
 ```
 
 ## Paper

python-package/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "py-perpetual"
-version = "0.3.1"
+version = "0.3.2"
 edition = "2021"
 authors = ["Mutlu Simsek <msimsek@perpetual-ml.com>"]
 homepage = "https://perpetual-ml.com"
@@ -19,7 +19,7 @@ crate-type = ["cdylib", "rlib"]
 
 [dependencies]
 pyo3 = { version = "0.21", features = ["extension-module"] }
-perpetual_rs = {package="perpetual", version = "0.3.1", path = "../" }
+perpetual_rs = {package="perpetual", version = "0.3.2", path = "../" }
 numpy = "0.21"
 ndarray = "0.15"
 serde_plain = { version = "1.0" }

python-package/pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "maturin"
 
 [project]
 name = "perpetual"
-version = "0.3.1"
+version = "0.3.2"
 description = "A self-generalizing gradient boosting machine which doesn't need hyperparameter optimization"
 license = { file = "LICENSE" }
 keywords = [

python-package/python/perpetual/data.py

@@ -1,5 +1,5 @@
 from dataclasses import dataclass
-from typing import Iterable
+from typing import Iterable, Optional, Union
 
 
 @dataclass
@@ -11,14 +11,14 @@ class Node:
     hessian_sum: float
     depth: int
     split_value: float
-    split_feature: int | str
+    split_feature: Union[str, int]
     split_gain: float
     missing_node: int
     left_child: int
     right_child: int
     is_leaf: bool
     node_type: str
     parent_node: int
-    generalization: float | None
-    left_categories: Iterable | None
-    right_categories: Iterable | None
+    generalization: Optional[float]
+    left_categories: Optional[Iterable]
+    right_categories: Optional[Iterable]