code: function mapChildren(children, func, context) {
    if (children == null) {
      return children;
    }
  
    var mapResult = {};
    var traverseContext = MapBookKeeping.getPooled(mapResult, func, context);
    traverseAllChildren(children, mapSingleChildIntoContext, traverseContext);
    MapBookKeeping.release(traverseContext);
    return ReactFragment.create(mapResult);
  }
docs: Maps children that are typically specified as `props.children`.
  
  The provided mapFunction(child, key, index) will be called for each
  leaf child.
  
  TODO: This may likely break any calls to `ReactChildren.map` that were
  previously relying on the fact that we guarded against null children.
  
  @param {?*} children Children tree container.
  @param {function(*, int)} mapFunction.
  @param {*} mapContext Context for mapFunction.
  @return {object} Object containing the ordered map of results.