code: function(initial_store, options) {
      if (store._store_created) {
        throw 'cannot create more than one global store'
      }
      for (let k in initial_store) {
        store._store[k] = initial_store[k]
      }
      if (options) {
        Object.assign(store.options, options)
      }
      store._store_created = true
    }
docs: Set the initial store. This can only be done once, and must be done before the
  store can be modified. This should be a JavaScript object with key/value pairs.
  This is the initial "hydration" of the store, and sets the expected types for all keys.
  @param {object} initial_store: Initial store object
  @param {object} options: options to apply to store