Python extension running really slow

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("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", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t, Column2 = _t, Column3 = _t, Column4 = _t]),
    #"Promoted Headers" = Table.PromoteHeaders(Source, [PromoteAllScalars=true]),
    #"Changed Type" = Table.TransformColumnTypes(#"Promoted Headers",{{"Entered Date", type datetime}}),
    #"Sorted Rows" = Table.Sort(#"Changed Type",{{"Ticket ID", Order.Ascending}, {"Entered Date", Order.Ascending}}),
    #"Added Index" = Table.AddIndexColumn(#"Sorted Rows", "Index", 0, 1, Int64.Type),
    #"Added Custom" = Table.AddColumn(#"Added Index", "Duration", each if [Index]=0 then null else if [Ticket ID]=#"Sorted Rows"[Ticket ID]{[Index]-1} then [Entered Date]-#"Sorted Rows"[Entered Date]{[Index]-1}  else null),
    #"Changed Type1" = Table.TransformColumnTypes(#"Added Custom",{{"Duration", type duration}})
in
    #"Changed Type1"

How to use this code: Create a new Blank Query. Click on "Advanced Editor". Replace the code in the window with the code provided here. Click "Done".