function listChildSubtrees(content, subtree, bottomRow) {
  const results = [];
  const branchingFactor = content._implicitTileset.branchingFactor;
  for (let i = 0; i < bottomRow.length; i++) {
    const leafTile = bottomRow[i];
    if (!defined(leafTile)) {
      continue;
    }

    for (let j = 0; j < branchingFactor; j++) {
      const index = i * branchingFactor + j;
      if (subtree.childSubtreeIsAvailableAtIndex(index)) {
        results.push({
          tile: leafTile,
          childIndex: j,
        });
      }
    }
  }
  return results;
}
Determine what child subtrees exist and return a list of information

@param {Implicit3DTileContent} content The implicit content
@param {ImplicitSubtree} subtree The subtree for looking up availability
@param {Array<Cesium3DTile|undefined>} bottomRow The bottom row of tiles in a transcoded subtree
@returns {ChildSubtreeLocator[]} A list of identifiers for the child subtrees.
@private