code: def potential_cloud_pixels(self):
          
          eq1 = self.basic_test()
          eq2 = self.whiteness_test()
          eq3 = self.hot_test()
          eq4 = self.nirswir_test()
          if self.sat == 'LC8':
              cir = self.cirrus_test()
              return (eq1 & eq2 & eq3 & eq4) | cir
          else:
              return eq1 & eq2 & eq3 & eq4
docs: Determine potential cloud pixels (PCPs)
          Combine basic spectral testsr to get a premliminary cloud mask
          First pass, section 3.1.1 in Zhu and Woodcock 2012
          Equation 6 (Zhu and Woodcock, 2012)
          Parameters
          ----------
          ndvi: ndarray
          ndsi: ndarray
          blue: ndarray
          green: ndarray
          red: ndarray
          nir: ndarray
          swir1: ndarray
          swir2: ndarray
          cirrus: ndarray
          tirs1: ndarray
          Output
          ------
          ndarray:
              potential cloud mask, boolean