docs: def get_mask(self, hdu=None, header=None, shape=None):
          """Create a 2-d mask.
  
          Parameters
          ----------
          hdu : `astropy.io.fits.ImageHDU`
              FITS image HDU
          header : `~astropy.io.fits.Header`
              FITS header
          shape : tuple
              Image shape
  
          Returns
          -------
          mask : `numpy.array`
              Boolean mask
  
          Examples
          --------
          get_mask(hdu=f[0])
          get_mask(shape=(10,10))
          get_mask(header=f[0].header, shape=(10,10))
          """
  
          if hdu and header is None:
              header = hdu.header
          if hdu and shape is None:
              shape = hdu.data.shape
  
          region_filter = self.get_filter(header=header)
          mask = region_filter.mask(shape)
  
          return mask