code: function findNestedBlocks (ast) {
    var tagged = [];
    traverse.traverse(ast, {
      enter: function (node, parent) {
        if (node.type === 'BlockStatement' && parent && parent.type === 'BlockStatement') {
          tagged.push([node, parent]);
        }
      }
    });
    return tagged;
  }
docs: Find BlockStatements which are direct children of BlockStatements.