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

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

xcollection/main.py

@@ -128,7 +128,6 @@ def __eq__(self, other: object) -> bool:
         return True
 
     def __repr__(self) -> str:
-
         output = ''.join(f'{unicode_key} {key}\n{repr(value)}\n\n' for key, value in self.items())
         return f'<{type(self).__name__} ({len(self)} keys)>\n{output}'
 
@@ -517,12 +516,10 @@ def _check_dim(self, dim: Optional[Union[Hashable, Iterable[Hashable]]]):
                 )
 
     def _implementation(self, func, dim, **kwargs) -> 'Collection':
-
         self._check_dim(dim)
 
         dataset_dict = {}
         for key, dataset in self.obj.items():
-
             dataset = dataset.map(func, dim=dim, **kwargs)
             dataset_dict[key] = dataset
         return Collection(dataset_dict)