code: function expandMemberExpression(str) {
    var segs = str.split(".");
    var expr = types.memberExpression(types.identifier(segs[0]), types.identifier(segs[1]));
    for (var i = 2; i < segs.length; i++) {
      expr = types.memberExpression(expr, types.identifier(segs[i]));
    }
    return expr;
  }
docs: Helper method that expands a dotted string into MemberExpression
  @param str
  @returns {*}