Add type definitions in prep for #6086 (#6090)

* Add type definitions in prep for #6086

#6086

Author: max-sixty

setup.cfg

@@ -198,6 +198,8 @@ ignore_missing_imports = True
 ignore_missing_imports = True
 [mypy-h5py.*]
 ignore_missing_imports = True
+[mypy-importlib_metadata.*]
+ignore_missing_imports = True
 [mypy-iris.*]
 ignore_missing_imports = True
 [mypy-matplotlib.*]

xarray/core/dataset.py

@@ -1068,14 +1068,14 @@ def persist(self, **kwargs) -> "Dataset":
     @classmethod
     def _construct_direct(
         cls,
-        variables,
-        coord_names,
-        dims=None,
-        attrs=None,
-        indexes=None,
-        encoding=None,
-        close=None,
-    ):
+        variables: Mapping[Any, Variable],
+        coord_names: Set[Hashable],
+        dims: Mapping[Any, int] = None,
+        attrs: Mapping = None,
+        indexes: Mapping[Any, Index] = None,
+        encoding: Mapping = None,
+        close: Callable[[], None] = None,
+    ) -> "Dataset":
         """Shortcut around __init__ for internal use when we want to skip
         costly validation
         """
@@ -2359,7 +2359,7 @@ def isel(
         indexers = drop_dims_from_indexers(indexers, self.dims, missing_dims)
 
         variables = {}
-        dims: Dict[Hashable, Tuple[int, ...]] = {}
+        dims: Dict[Hashable, int] = {}
         coord_names = self._coord_names.copy()
         indexes = self._indexes.copy() if self._indexes is not None else None