/// <summary>
/// Applies a FlatMap transformation on a <see cref="DataStream{T}"/>. The transformation calls a <see cref="IFlatMapFunction{TInput,TOutput}"/> for each element of the DataStream. Each FlatMapFunction call can return any number of elements including none. The user can also extend <see cref="IRichFunction"/> to gain access to other features provided by the <see cref="IRichFunction"/> interface.
/// </summary>
/// <typeparam name="TOutput">The output type.</typeparam>
/// <param name="flatMapper">The MapFunction that is called for each element of the DataStream.</param>
/// <returns>The transformed <see cref="DataStream{T}"/>.</returns>
public SingleOutputStreamOperator <TOutput> FlatMap <TOutput>(IFlatMapFunction <TElement, TOutput> flatMapper)
{
var outType = TypeExtractor.GetFlatMapReturnTypes(Clean(flatMapper), Type, Utils.GetCallLocationName(), true);
return(Transform("Flat Map", outType, new StreamFlatMap <TElement, TOutput>(Clean(flatMapper))));
}