docs: def get_z(self, var, coords=None):
          """
          Get the vertical (z-) coordinate of a variable
  
          This method searches for the z-coordinate in the :attr:`ds`. It first
          checks whether there is one dimension that holds an ``'axis'``
          attribute with 'Z', otherwise it looks whether there is an intersection
          between the :attr:`z` attribute and the variables dimensions, otherwise
          it returns the coordinate corresponding to the third last dimension of
          `var` (or the second last or last if var is two or one-dimensional)
  
          Possible types
          --------------
          var: xarray.Variable
              The variable to get the z-coordinate for
          coords: dict
              Coordinates to use. If None, the coordinates of the dataset in the
              :attr:`ds` attribute are used.
  
          Returns
          -------
          xarray.Coordinate or None
              The z-coordinate or None if no z coordinate could be found"""
          coords = coords or self.ds.coords
          coord = self.get_variable_by_axis(var, 'z', coords)
          if coord is not None:
              return coord
          zname = self.get_zname(var)
          if zname is not None:
              return coords.get(zname)
          return None