Define() - Is there a way to define the define()?

*[_type == "resource"] {
  _id,
    "slug": slug.current,
    title,
    defined(subtitle) => {subtitle},
    defined(content) => {content},
    description,
    defined(keywords) => {keywords},
    defined(video.url) => {"video": video.url},
    "asset": {
      defined(external) => {"external": asset.external},
      defined(internal) => {"internal": asset.internal.asset->url}
    },
    categories[]->{_id, title},
   "poster": poster.asset-> {
     ...,
     "lqip": metadata.lqip
   }
}