code: def get_xyz(self, list_of_names=None):
          
          if list_of_names is not None:
              filter_lambda = lambda x: x['name'] in list_of_names
          else:
              filter_lambda = None
  
          return self.electrodes.get(filter_lambda=filter_lambda,
                                     map_lambda=lambda e: (float(e['x']),
                                                           float(e['y']),
                                                           float(e['z'])))
docs: Get xyz coordinates for these electrodes
  
          Parameters
          ----------
          list_of_names : list of str
              list of electrode names to use
  
          Returns
          -------
          list of tuples of 3 floats (x, y, z)
              list of xyz coordinates for all the electrodes
  
          TODO
          ----
          coordinate system of electrodes