code: def add_circles(self, ra_cen, dec_cen, radius, depth=None):
          
          if depth is None or depth > self.maxdepth:
              depth = self.maxdepth
          try:
              sky = list(zip(ra_cen, dec_cen))
              rad = radius
          except TypeError:
              sky = [[ra_cen, dec_cen]]
              rad = [radius]
          sky = np.array(sky)
          rad = np.array(rad)
          vectors = self.sky2vec(sky)
          for vec, r in zip(vectors, rad):
              pix = hp.query_disc(2**depth, vec, r, inclusive=True, nest=True)
              self.add_pixels(pix, depth)
          self._renorm()
          return
docs: Add one or more circles to this region
  
          Parameters
          ----------
          ra_cen, dec_cen, radius : float or list
              The center and radius of the circle or circles to add to this region.
  
          depth : int
              The depth at which the given circles will be inserted.