insertAt(index, ...values) {
    if (this.context) {
      this.context.splice(this.path, index, 0, values)
    } else if (!this[OBJECT_ID]) {
      this.elems.splice(index, 0, ...values.map(value => ({value})))
    } else {
      throw new TypeError('Automerge.Text object cannot be modified outside of a change block')
    }
    return this
  }
Inserts new list items `values` starting at position `index`.