/// <summary>
/// Gets and enumerable of opened <see cref="OrderTicket"/> matching the specified <paramref name="filter"/>
/// </summary>
/// <param name="filter">The filter predicate used to find the required order tickets</param>
/// <returns>An enumerable of opened <see cref="OrderTicket"/> matching the specified <paramref name="filter"/></returns>
public IEnumerable <OrderTicket> GetOpenOrderTickets(Func <OrderTicket, bool> filter = null)
{
return(_orderProcessor.GetOpenOrderTickets(filter ?? (x => true)));
}