old_contents: // Copyright (c) 2017 The Regents of the University of Michigan.
  // All Rights Reserved. Licensed according to the terms of the Revised
  // BSD License. See LICENSE.txt for details.
  
  module.exports = function() {
    log_tree = {
      description: "",
  
      num: () => 0,
      den: () => 1
    };
  
    log_tree[Symbol.iterator] = function*() {};
  
    return log_tree;
  };
  
new_contents: // Copyright (c) 2017 The Regents of the University of Michigan.
  // All Rights Reserved. Licensed according to the terms of the Revised
  // BSD License. See LICENSE.txt for details.
  
  module.exports = function() {
    log_tree = { };
  
    log_tree.description = "";
    log_tree.num = () => 0;
    log_tree.den = () => 1;
  
    log_tree[Symbol.iterator] = function*() {};
  
    return log_tree;
  };
  
subject: Define all log_tree members after definition