[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Author: pre-commit-ci[bot]

xarray/core/dataset.py

@@ -4772,9 +4772,7 @@ def expand_dims(
             if d in self.dims:
                 raise ValueError(f"Dimension {d} already exists.")
             if d in self._variables and not utils.is_scalar(self._variables[d]):
-                raise ValueError(
-                    f"{d} already exists as coordinate or variable name."
-                )
+                raise ValueError(f"{d} already exists as coordinate or variable name.")
 
         variables: dict[Hashable, Variable] = {}
         indexes: dict[Hashable, Index] = dict(self._indexes)