code: function getRootBlock() {
    var blocks = mainWorkspace.getTopBlocks(false);
    for (var i = 0, block; block = blocks[i]; i++) {
      if (block.type == 'factory_base') {
        return block;
      }
    }
    return null;
  }
docs: Return the uneditable container block that everything else attaches to.
  @return {Blockly.Block}