getMonkey(path) {
    path = coercePath(path);

    const monkey = getIn(this._monkeys, [].concat(path)).data;

    if (monkey instanceof Monkey)
      return monkey;

    return null;
  }
Method returning a monkey at the given path or else `null`.

@param  {path}        path - Path of the monkey to retrieve.
@return {Monkey|null}      - The Monkey instance of `null`.