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'use strict';
const _modifiedPaths = require('../common').modifiedPaths;
/** * Given an update document with potential update operators (`$set`, etc.) * returns an object whose keys are the directly modified paths. * * If there are any top-level keys that don't start with `$`, we assume those * will get wrapped in a `$set`. The Mongoose Query is responsible for wrapping * top-level keys in `$set`. * * @param {Object} update * @return {Object} modified */
module.exports = function modifiedPaths(update) {  const keys = Object.keys(update);  const res = {};
  const withoutDollarKeys = {};  for (const key of keys) {    if (key.startsWith('$')) {      _modifiedPaths(update[key], '', res);      continue;    }    withoutDollarKeys[key] = update[key];  }
  _modifiedPaths(withoutDollarKeys, '', res);
  return res;};