Data.re

module Models = {
  type actor = {
    id: int,
    name: string,
    character: option(string),
    link: string,
    thumbnail: option(string),
    hash: string,
    seen: list(watchable),
    watchables: list(watchable),
  }
  [@bs.deriving abstract]
  and watchable = {
    id: int,
    identifier: option(string),
    name: string,
    overview: option(string),
    show: option(string),
    link: string,
    actors: list(actor),
    released_at: option(string),
    watched_at: option(string),
    credit: option(string),
    type_: string,
  };
};

module Decode = {
  let emptyToOption = value => value === "" ? None : Some(value);
  let optionalNullableField = (key, json) : option(string) =>
    Json.Decode.(json |> field(key, nullable(string)) |> Js.nullToOption);

  let rec watchable = json : Models.watchable =>
    Json.Decode.{
      id: json |> field("id", int),
      identifier: json |> optional(field("identifier", string)),
      name: json |> field("name", string),
      overview: json |> optionalNullableField("overview"),
      link: json |> field("link", string),
      released_at: json |> optionalNullableField("released_at"),
      watched_at: json |> optionalNullableField("watched_at"),
      credit: json |> optional(field("credit", string)),
      show: json |> optional(field("show", string)),
      actors: json |> field("actors", list(actor)),
      type_: json |> field("type", string),
    }
  and actor = json : Models.actor =>
    Json.Decode.{
      id: json |> field("id", int),
      name: json |> field("name", string),
      character: json |> optional(field("character", string)),
      link: json |> field("link", string),
      thumbnail: json |> field("thumbnail", string) |> emptyToOption,
      hash: json |> field("hash", string),
      seen: json |> field("seen", list(watchable)),
      watchables: json |> field("watchables", list(watchable)),
    };
};

what does the "and" keyword mean?