get externalRelations() {
    const externalRelations = [];
    const seenAssets = new Set();
    (function gatherExternalRelations(asset) {
      if (asset.keepUnpopulated || seenAssets.has(asset)) {
        return;
      }
      seenAssets.add(asset);
      for (const outgoingRelation of asset.outgoingRelations) {
        if (outgoingRelation.to.isInline) {
          gatherExternalRelations(outgoingRelation.to);
        } else {
          externalRelations.push(outgoingRelation);
        }
      }
    })(this);
    return externalRelations;
  }
The subset of outgoing Relations that point to external (non-inlined) Assets

@type {Relation[]}