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))

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