code: def return_xy(self, labels=None):
          
          xyz = self.return_xyz(labels=labels)
          xy = asarray(xyz)[:, 1:]
          return xy
docs: Returns the location in xy for some channels.
  
          Parameters
          ----------
          labels : list of str, optional
              the names of the channels.
  
          Returns
          -------
          numpy.ndarray
              a 2xn vector with the position of a channel.
  
          Notes
          -----
          Simplest implementation. We should at least use project onto a 2D plane