code: function manager(map, key) {
    if (!(key instanceof Object)) {
      throw new TypeError('Key must be an object')
    }
  
    let contents = map.get(key)
  
    if (!contents) {
      map.set(key, contents = {})
    }
  
    return contents
  }
docs: Local scope manager
  
  Use this function to assign private properties related to your objects / class instances.
  
  @param   {WeakMap} map     The WeakMap to which the private scope objects should be saved.
  You should not provide this parameter - it is bound automatically for
  you. Just use the key below.
  @param   {Object}  key     The key with which to associate this scope
  @return  {Object}          Object which can be used to assign properties to