Fix mypy issues

Author: VeckoTheGecko

src/parcels/_core/model.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
-from collections.abc import Mapping, Sequence
+from collections.abc import Hashable, Sequence
 from typing import Any, Self
 
 import cf_xarray  # noqa: F401
@@ -34,7 +34,7 @@
 )
 from parcels.interpolators._base import ScalarInterpolator, VectorInterpolator
 
-TVectorFieldMapping = Mapping[str, tuple[str, str] | tuple[str, str, str]]
+TVectorFieldMapping = dict[str, tuple[str, str] | tuple[str, str, str]]
 
 
 class ModelData(ABC):
@@ -126,7 +126,7 @@ def construct_fields(self) -> list[Field | VectorField]:
             )
 
             component_fields = [single_fields[name] for name in components]
-            vector_fields[vfield_name] = VectorField(vfield_name, *component_fields, interp_method=interp_method)
+            vector_fields[vfield_name] = VectorField(vfield_name, *component_fields, interp_method=interp_method)  # type:ignore[misc,arg-type]
 
         fields: dict[str, Field | VectorField] = {**single_fields, **vector_fields}
         return list(fields.values())
@@ -178,7 +178,7 @@ def resolve_vector_fields(
     if vector_fields is None:
         return {}
     if vector_fields is NOTSET:  # i.e., the default vectorfield discovery behaviour
-        return _default_vector_field_components(ds.data_vars)
+        return _default_vector_field_components(list(ds.data_vars))
     return vector_fields
 
 
@@ -247,7 +247,7 @@ def construct_fields(self) -> list[Field | VectorField]:
             interp_method = Ux_Velocity()
 
             component_fields = [single_fields[name] for name in components]
-            vector_fields[vfield_name] = VectorField(vfield_name, *component_fields, interp_method=interp_method)
+            vector_fields[vfield_name] = VectorField(vfield_name, *component_fields, interp_method=interp_method)  # type:ignore[misc, arg-type]
 
         fields: dict[str, Field | VectorField] = {**single_fields, **vector_fields}
         return list(fields.values())
@@ -304,9 +304,9 @@ def _get_mesh_type_from_sgrid_dataset(ds_sgrid: xr.Dataset) -> Mesh:
     return "spherical" if _is_coordinate_in_degrees(ds_sgrid[fpoint_x]) else "flat"
 
 
-def _default_vector_field_components(data_vars: Sequence[str]) -> TVectorFieldMapping:
+def _default_vector_field_components(data_vars: Sequence[Hashable]) -> TVectorFieldMapping:
     vars = set(data_vars)
-    ret = {}
+    ret: TVectorFieldMapping = {}
 
     if {"U", "V"}.issubset(vars):
         ret["UV"] = ("U", "V")