old_contents: import { select } from 'd3-selection';
  import Set from 'es6-set';
  
  let namespaces = new Set();
  
  const makeEnum = (ns, keys) => {
    // Construct an object containing keys matching those passed in `keys`, whose
    // values are the keys themselves, prefixed by the specified namespace.
    //
    // Dots are not allowed in the namespace name.
    if (ns.indexOf('.') > -1) {
      throw new Error('dots not allowed in namespace');
    }
  
    // Namespaces are not allowed to repeat.
    if (namespaces.has(ns)) {
      throw new Error(`duplicate namespace "${ns}"`);
    }
    namespaces.add(ns);
  
    let obj = {};
  
    let used = new Set();
    keys.forEach((key) => {
      if (key.indexOf('.') > -1) {
        throw new Error('dots not allowed in key');
      }
  
      if (used.has(key)) {
        throw new Error(`duplicate key "${key}"`);
      }
      used.add(key);
  
      obj[key] = `${ns}.${key}`;
    });
  
    // Freeze the resulting object so no one else can alter the values or keys.
    return Object.freeze(obj);
  };
  
  const enumName = (enumVal) => enumVal.split('.')[0];
  const enumValue = (enumVal) => enumVal.split('.')[1];
  
  const switchOverlay = (which) => {
    select('#overlay')
      .style('display', which === null ? 'none' : null)
      .selectAll('.overlay')
      .style('display', function () {
        return select(this).classed(which) ? null : 'none';
      });
  };
  
  const initializeNewProject = () => {
    return Promise.resolve({
      name: 'Foobarius'
    });
  };
  
  export {
    makeEnum,
    enumName,
    enumValue,
    switchOverlay,
    initializeNewProject
  };
  
new_contents: import { select } from 'd3-selection';
  import Set from 'es6-set';
  
  let namespaces = new Set();
  
  const makeEnum = (ns, keys) => {
    // Construct an object containing keys matching those passed in `keys`, whose
    // values are the keys themselves, prefixed by the specified namespace.
    //
    // Dots are not allowed in the namespace name.
    if (ns.indexOf('.') > -1) {
      throw new Error('dots not allowed in namespace');
    }
  
    // Namespaces are not allowed to repeat.
    if (namespaces.has(ns)) {
      throw new Error(`duplicate namespace "${ns}"`);
    }
    namespaces.add(ns);
  
    let obj = {};
  
    let used = new Set();
    keys.forEach((key) => {
      if (key.indexOf('.') > -1) {
        throw new Error('dots not allowed in key');
      }
  
      if (used.has(key)) {
        throw new Error(`duplicate key "${key}"`);
      }
      used.add(key);
  
      obj[key] = `${ns}.${key}`;
    });
  
    // Freeze the resulting object so no one else can alter the values or keys.
    return Object.freeze(obj);
  };
  
  const enumName = (enumVal) => enumVal.split('.')[0];
  const enumValue = (enumVal) => enumVal.split('.')[1];
  
  const switchOverlay = (which) => {
    select('#overlay')
      .style('display', which === null ? 'none' : null)
      .selectAll('.overlay')
      .style('display', function () {
        return select(this).classed(which) ? null : 'none';
      });
  };
  
  const initializeNewProject = () => {
    console.log('stub function: initializeNewProject');
    return Promise.resolve({
      name: 'Foobarius'
    });
  };
  
  export {
    makeEnum,
    enumName,
    enumValue,
    switchOverlay,
    initializeNewProject
  };
  
subject: Include a console message to mark the stub function