code: function relativeModuleSource(from, to) {
    const p = join(
      relative(path.dirname(from), path.dirname(to)),
      path.basename(to).replace(/\.\w+$/, ''),
    );
  
    if (!_.startsWith(p, '.')) return './' + p;
    return p;
  }
docs: get the module source of 'to' from 'from' file. e.g: import to from '../to';