code: def circular(cls, shape, pixel_scale, radius_arcsec, centre=(0., 0.), invert=False):
          
          mask = mask_util.mask_circular_from_shape_pixel_scale_and_radius(shape, pixel_scale, radius_arcsec,
                                                                           centre)
          if invert: mask = np.invert(mask)
          return cls(array=mask.astype('bool'), pixel_scale=pixel_scale)
docs: Setup a mask where unmasked pixels are within a circle of an input arc second radius and centre.
  
          Parameters
          ----------
          shape: (int, int)
              The (y,x) shape of the mask in units of pixels.
          pixel_scale: float
              The arc-second to pixel conversion factor of each pixel.
          radius_arcsec : float
              The radius (in arc seconds) of the circle within which pixels unmasked.
          centre: (float, float)
              The centre of the circle used to mask pixels.