inline() {
    if (
      this.to.isAsset &&
      this.to.incomingRelations.filter((r) => r._to !== r.from).length > 1
    ) {
      // This isn't the only incoming relation to the asset, clone before inlining.
      this.to.clone(this);
    }
    this.to.incomingInlineRelation = this;
    if (!this.to.isInline) {
      this.to.url = null;
    }
    return this;
  }
Inline the relation. This is only supported by certain relation
types and will produce different results depending on the type
(`data:` url, inline script, inline stylesheet...).

Will make a clone of the target asset if it has more incoming
relations than this one.

@return {Relation} The relation itself (chaining-friendly).