Update Self from typing_extensions, for Python 3.10

Author: psomhorst

eitprocessing/datahandling/pixelmap.py

@@ -29,7 +29,7 @@
 from collections.abc import Callable
 from copy import deepcopy
 from dataclasses import KW_ONLY, MISSING, asdict, dataclass, field, replace
-from typing import Self, TypeVar, cast
+from typing import TypeVar, cast
 
 import matplotlib as mpl
 import numpy as np
@@ -41,6 +41,7 @@
 from matplotlib.image import AxesImage
 from matplotlib.ticker import PercentFormatter
 from numpy import typing as npt
+from typing_extensions import Self
 
 from eitprocessing.plotting.helpers import AbsolutePercentFormatter, AbsoluteScalarFormatter