code: def _assert_equal_channels(axis):
      
      for i0 in axis:
          for i1 in axis:
              if not all(i0 == i1):
                  raise ValueError('The channels for all the trials should have '
                                   'the same labels, in the same order.')
docs: check that all the trials have the same channels, in the same order.
  
      Parameters
      ----------
      axis : ndarray of ndarray
          one of the data axis
  
      Raises
      ------