code: def assign_coords(self, **kwargs):
          
          data = self.copy(deep=False)
          results = self._calc_assign_results(kwargs)
          data.coords.update(results)
          return data
docs: Assign new coordinates to this object.
  
          Returns a new object with all the original data in addition to the new
          coordinates.
  
          Parameters
          ----------
          kwargs : keyword, value pairs
              keywords are the variables names. If the values are callable, they
              are computed on this object and assigned to new coordinate
              variables. If the values are not callable, (e.g. a DataArray,
              scalar, or array), they are simply assigned.
  
          Returns
          -------
          assigned : same type as caller
              A new object with the new coordinates in addition to the existing
              data.
  
          Examples
          --------
  
          Convert longitude coordinates from 0-359 to -180-179:
  
          >>> da = xr.DataArray(np.random.rand(4),
          ...                   coords=[np.array([358, 359, 0, 1])],
          ...                   dims='lon')
          >>> da
          <xarray.DataArray (lon: 4)>
          array([0.28298 , 0.667347, 0.657938, 0.177683])
          Coordinates:
            * lon      (lon) int64 358 359 0 1
          >>> da.assign_coords(lon=(((da.lon + 180) % 360) - 180))
          <xarray.DataArray (lon: 4)>
          array([0.28298 , 0.667347, 0.657938, 0.177683])
          Coordinates:
            * lon      (lon) int64 -2 -1 0 1
  
          Notes
          -----
          Since ``kwargs`` is a dictionary, the order of your arguments may not
          be preserved, and so the order of the new variables is not well
          defined. Assigning multiple variables within the same ``assign_coords``
          is possible, but you cannot reference other variables created within
          the same ``assign_coords`` call.
  
          See also
          --------
          Dataset.assign
          Dataset.swap_dims