Delete unused variable

roseau/load_flow_single/models/line_parameters.py

@@ -1,13 +1,12 @@
 import logging
 import re
 from pathlib import Path
-from typing import Literal, NoReturn, TypeAlias, TypeVar
+from typing import Literal, NoReturn
 
 import numpy as np
 import pandas as pd
 from typing_extensions import Self
 
-from roseau.load_flow._compat import StrEnum
 from roseau.load_flow.exceptions import RoseauLoadFlowException, RoseauLoadFlowExceptionCode
 from roseau.load_flow.models import LineParameters as MultiLineParameters
 from roseau.load_flow.typing import Complex, Float, Id, JsonDict
@@ -17,9 +16,6 @@
 logger = logging.getLogger(__name__)
 
 
-_StrEnumType: TypeAlias = TypeVar("_StrEnumType", bound=StrEnum)
-
-
 class LineParameters(Identifiable, JsonMixin, CatalogueMixin[pd.DataFrame]):
     """Parameters that define electrical models of lines."""