IAggregateFluent<TNewResult> Lookup<TNewResult>(
	string from,
	FieldDefinition<TResult> localField,
	FieldDefinition<BsonDocument> foreignField,
	FieldDefinition<TNewResult> as,
	IBsonSerializer<TNewResult> newResultSerializer = null
)

Function Lookup(Of TNewResult) ( 
	from As String,
	localField As FieldDefinition(Of TResult),
	foreignField As FieldDefinition(Of BsonDocument),
	as As FieldDefinition(Of TNewResult),
	Optional newResultSerializer As IBsonSerializer(Of TNewResult) = Nothing
) As IAggregateFluent(Of TNewResult)

abstract Lookup : 
        from : string * 
        localField : FieldDefinition<'TResult> * 
        foreignField : FieldDefinition<BsonDocument> * 
        as : FieldDefinition<'TNewResult> * 
        ?newResultSerializer : IBsonSerializer<'TNewResult> 
(* Defaults:
        let _newResultSerializer = defaultArg newResultSerializer null
*)
-> IAggregateFluent<'TNewResult>