code: def mean(data, channels=None):
      
      # Slice data to take statistics from
      if channels is None:
          data_stats = data
      else:
          data_stats = data[:, channels]
  
      # Calculate and return statistic
      return np.mean(data_stats, axis=0)
docs: Calculate the mean of the events in an FCSData object.
  
      Parameters
      ----------
      data : FCSData or numpy array
          NxD flow cytometry data where N is the number of events and D is
          the number of parameters (aka channels).
      channels : int or str or list of int or list of str, optional
          Channels on which to calculate the statistic. If None, use all
          channels.
  
      Returns
      -------
      float or numpy array
          The mean of the events in the specified channels of `data`.