docs: def spatialBin(self, roi):
          """
          Calculate indices of ROI pixels corresponding to object locations.
          """
          if hasattr(self,'pixel_roi_index') and hasattr(self,'pixel'): 
              logger.warning('Catalog alread spatially binned')
              return
  
          # ADW: Not safe to set index = -1 (since it will access last entry); 
          # np.inf would be better...
          self.pixel = ang2pix(self.config['coords']['nside_pixel'],self.lon,self.lat)
          self.pixel_roi_index = roi.indexROI(self.lon,self.lat)
  
          logger.info("Found %i objects outside ROI"%(self.pixel_roi_index < 0).sum())