masks' _include should be able to operate without data being given (masks are defined with or without data to mask)
masks' _include should be able to operate without data being given
(masks are defined with or without data to mask)

e-koch/spectral-cube,radio-astro-tools/spectral-cube,jzuhone/spectral-cube,keflavich/spectral-cube,low-sky/spectral-cube