Remove 3.8 syntax (#41)

* Add requires line to pyproject.toml.

* Remove typing module in remaining files.

* Fix bug that refactors two incorrect type.

* Change import style for collections.abc.

auglib/core/interface.py

@@ -1,5 +1,7 @@
+from __future__ import annotations
+
+from collections.abc import Sequence
 import os
-import typing
 
 import numpy as np
 import pandas as pd
@@ -140,10 +142,10 @@ def __init__(
         *,
         sampling_rate: int = None,
         resample: bool = False,
-        channels: typing.Union[int, typing.Sequence[int]] = None,
+        channels: int | Sequence[int] = None,
         mixdown: bool = False,
         keep_nat: bool = False,
-        num_workers: typing.Optional[int] = 1,
+        num_workers: int | None = 1,
         multiprocessing: bool = False,
         seed: int = None,
         verbose: bool = False,
@@ -184,15 +186,15 @@ def short_id(
 
     def augment(
         self,
-        data: typing.Union[pd.Index, pd.Series, pd.DataFrame],
+        data: pd.Index | pd.Series | pd.DataFrame,
         cache_root: str = None,
         *,
         data_root: str = None,
         remove_root: str = None,
         modified_only: bool = True,
         num_variants: int = 1,
         force: bool = False,
-    ) -> typing.Union[pd.Index, pd.Series, pd.DataFrame]:
+    ) -> pd.Index | pd.Series | pd.DataFrame:
         r"""Augment an index, column, or table conform to audformat.
 
         Creates ``num_variants`` copies of the segments referenced in the index
@@ -505,10 +507,10 @@ def _apply_nat_mask(
 
 
 def _augmented_files(
-    files: typing.Sequence[str],
+    files: Sequence[str],
     cache_root: str,
     remove_root: str = None,
-) -> typing.List[str]:
+) -> list[str]:
     r"""Return destination path for augmented files.
 
     If files contain the same filename several times,

auglib/core/observe.py

@@ -1,5 +1,7 @@
+from __future__ import annotations
+
+from collections.abc import MutableSequence
 import random
-import typing
 
 import numpy as np
 
@@ -13,7 +15,7 @@ class Base(audobject.Object):
 
     """
 
-    def __call__(self) -> typing.Any:  # pragma: no cover
+    def __call__(self) -> object:  # pragma: no cover
         r"""Observe next value.
 
         Returns:
@@ -227,7 +229,7 @@ class List(Base):
     )
     def __init__(
         self,
-        elements: typing.MutableSequence[typing.Any],
+        elements: MutableSequence[object],
         *,
         shuffle: bool = False,
         draw: bool = False,
@@ -241,10 +243,10 @@ def __init__(
         self._counter = 0
         self._iter = False
 
-    def _draw(self) -> typing.Any:
+    def _draw(self) -> object:
         return self.elements[random.randint(0, len(self) - 1)]
 
-    def _next(self) -> typing.Any:
+    def _next(self) -> object:
         if self.shuffle and self._counter == 0:
             random.shuffle(self.elements)
         element = self.elements[self._counter]
@@ -254,7 +256,7 @@ def _next(self) -> typing.Any:
             self._iter = False
         return element
 
-    def __call__(self) -> typing.Any:
+    def __call__(self) -> object:
         r"""Observe next value from list.
 
         Returns:
@@ -281,8 +283,8 @@ def __next__(self):  # noqa: D105
 
 
 def observe(
-    x: typing.Union[typing.Any, Base],
-) -> typing.Any:
+    x: object | Base,
+) -> object:
     r"""Convenient function to observe a value.
 
     Returns ``x()`` if ``x`` is of type :class:`auglib.observe.Base`,

auglib/core/resolver.py

@@ -1,4 +1,4 @@
-import typing
+from collections.abc import MutableSequence
 
 import numpy as np
 
@@ -10,14 +10,14 @@ class ArrayResolver(audobject.resolver.Base):
 
     def decode(
         self,
-        value: typing.Any,
-    ) -> typing.Any:
+        value: object,
+    ) -> object:
         return value
 
     def encode(
         self,
-        value: typing.Any,
-    ) -> typing.Any:
+        value: object,
+    ) -> object:
         if isinstance(value, np.ndarray):
             raise ValueError(
                 f"Cannot serialize an instance of "
@@ -37,14 +37,14 @@ class ObservableListResolver(audobject.resolver.Base):
 
     def decode(
         self,
-        value: typing.Any,
-    ) -> typing.Any:
+        value: object,
+    ) -> object:
         return value
 
     def encode(
         self,
-        value: typing.MutableSequence[typing.Any],
-    ) -> typing.Any:
+        value: MutableSequence[object],
+    ) -> object:
         for v in value:
             if isinstance(v, np.ndarray):
                 raise ValueError(

auglib/core/time.py

@@ -1,4 +1,4 @@
-import typing
+from __future__ import annotations
 
 import pandas as pd
 
@@ -43,7 +43,7 @@ class Time(audobject.Object):
 
     def __init__(
         self,
-        value: typing.Union[int, float, observe.Base],
+        value: int | float | observe.Base,
         unit: str,
     ):
         self.value = value