code: def add_pixels(self, pix, depth):
          
          if depth not in self.pixeldict:
              self.pixeldict[depth] = set()
          self.pixeldict[depth].update(set(pix))
docs: Add one or more HEALPix pixels to this region.
  
          Parameters
          ----------
          pix : int or iterable
              The pixels to be added
  
          depth : int
              The depth at which the pixels are added.