code: function getPeerDependencies(moduleName) {
      let result = getPeerDependencies.cache.get(moduleName);
  
      if (!result) {
          log.info(`Checking peerDependencies of ${moduleName}`);
  
          result = npmUtils.fetchPeerDependencies(moduleName);
          getPeerDependencies.cache.set(moduleName, result);
      }
  
      return result;
  }
docs: Get the peer dependencies of the given module.
  This adds the gotten value to cache at the first time, then reuses it.
  In a process, this function is called twice, but `npmUtils.fetchPeerDependencies` needs to access network which is relatively slow.
  @param {string} moduleName The module name to get.
  @returns {Object} The peer dependencies of the given module.
  This object is the object of `peerDependencies` field of `package.json`.
  Returns null if npm was not found.