docs: def isel_variable_and_index(
      name: Hashable,
      variable: Variable,
      index: pd.Index,
      indexers: Mapping[Any, Union[slice, Variable]],
  ) -> Tuple[Variable, Optional[pd.Index]]:
      """Index a Variable and pandas.Index together."""
      if not indexers:
          # nothing to index
          return variable.copy(deep=False), index
  
      if len(variable.dims) > 1:
          raise NotImplementedError(
              'indexing multi-dimensional variable with indexes is not '
              'supported yet')
  
      new_variable = variable.isel(indexers)
  
      if new_variable.dims != (name,):
          # can't preserve a index if result has new dimensions
          return new_variable, None
  
      # we need to compute the new index
      (dim,) = variable.dims
      indexer = indexers[dim]
      if isinstance(indexer, Variable):
          indexer = indexer.data
      new_index = index[indexer]
      return new_variable, new_index