docs: def sigmafilter(data, sigmas, passes):
      """Remove datapoints outside of a specified standard deviation range."""
      for n in range(passes):
          meandata = np.mean(data[~np.isnan(data)])
          sigma = np.std(data[~np.isnan(data)])
          data[data > meandata+sigmas*sigma] = np.nan
          data[data < meandata-sigmas*sigma] = np.nan
      return data