code: def potential_snow_layer(self):
          
          return (self.ndsi > 0.15) & (self.tirs1 < 9.85) & (self.nir > 0.11) & (self.green > 0.1)
docs: Spectral test to determine potential snow
          Uses the 9.85C (283K) threshold defined in Zhu, Woodcock 2015
          Parameters
          ----------
          ndsi: ndarray
          green: ndarray
          nir: ndarray
          tirs1: ndarray
          Output
          ------
          ndarray:
              boolean, True is potential snow