GridFSUploadStream OpenUploadStream(
	string filename,
	GridFSUploadOptions options = null,
	CancellationToken cancellationToken = null
)

Function OpenUploadStream ( 
	filename As String,
	Optional options As GridFSUploadOptions = Nothing,
	Optional cancellationToken As CancellationToken = Nothing
) As GridFSUploadStream

abstract OpenUploadStream : 
        filename : string * 
        ?options : GridFSUploadOptions * 
        ?cancellationToken : CancellationToken 
(* Defaults:
        let _options = defaultArg options null
        let _cancellationToken = defaultArg cancellationToken null
*)
-> GridFSUploadStream