docs: def _get_reference_band(self, data):
          """ Extract the max-ratio band from time-series
  
              The max-ratio is defined as max(NIR,SWIR1)/BLUE
  
              :param data: 4D array from which to compute the max-ratio reference band
              :type data: numpy array
              :return: 3D array containing the max-ratio reference band
          """
          blue = data[..., self.blue_idx].astype("float32")
          nir = data[..., self.nir_idx].astype("float32")
          swir1 = data[..., self.swir1_idx].astype("float32")
          return np.nanmax(np.array([nir, swir1]), axis=0) / blue