docs: def groupby(self, group, squeeze: bool = True):
          """Returns a GroupBy object for performing grouped operations.
  
          Parameters
          ----------
          group : str, DataArray or IndexVariable
              Array whose unique values should be used to group this array. If a
              string, must be the name of a variable contained in this dataset.
          squeeze : boolean, optional
              If "group" is a dimension of any arrays in this dataset, `squeeze`
              controls whether the subarrays have a dimension of length 1 along
              that dimension or if the dimension is squeezed out.
  
          Returns
          -------
          grouped : GroupBy
              A `GroupBy` object patterned after `pandas.GroupBy` that can be
              iterated over in the form of `(unique_value, grouped_array)` pairs.
  
          Examples
          --------
          Calculate daily anomalies for daily data:
  
          >>> da = xr.DataArray(np.linspace(0, 1826, num=1827),
          ...                   coords=[pd.date_range('1/1/2000', '31/12/2004',
          ...                           freq='D')],
          ...                   dims='time')
          >>> da
          <xarray.DataArray (time: 1827)>
          array([0.000e+00, 1.000e+00, 2.000e+00, ..., 1.824e+03, 1.825e+03, 1.826e+03])
          Coordinates:
            * time     (time) datetime64[ns] 2000-01-01 2000-01-02 2000-01-03 ...
          >>> da.groupby('time.dayofyear') - da.groupby('time.dayofyear').mean('time')
          <xarray.DataArray (time: 1827)>
          array([-730.8, -730.8, -730.8, ...,  730.2,  730.2,  730.5])
          Coordinates:
            * time       (time) datetime64[ns] 2000-01-01 2000-01-02 2000-01-03 ...
              dayofyear  (time) int64 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 ...
  
          See Also
          --------
          core.groupby.DataArrayGroupBy
          core.groupby.DatasetGroupBy
          """  # noqa
          return self._groupby_cls(self, group, squeeze=squeeze)