Power Query M - Text Cleaner

/*
    Created By: Alex Powers
    Website: http://www.itsnotaboutthecell.com
    LinkedIn: https://www.linkedin.com/in/alexmpowers/
    Contact: alexmpowers@itsnotaboutthecell.com
    Reference: https://www.excelguru.ca/blog/2018/10/17/analyzing-text-with-power-query-and-excel/?fbclid=IwAR1t-emFdo7Wt0cnNMuM5W4njwhbxftcRku3GUzPzYQOyGeb0sgb-kbKMhU

*/

(Sentence as text) as text =>
let
    characterList = {97..122, 32, 33, 66, 42, 44, 46},
    Source = Table.FromList(Text.ToList(Sentence), Splitter.SplitByNothing(), type table [Letter = text], null, ExtraValues.Error),
    #"Valid Character" = Table.AddColumn(Source, "Valid Character", each List.Contains(characterList, Character.ToNumber(Text.Lower([Letter]))), type logical),
    #"Filtered Rows: Valid Character = true" = Table.SelectRows(#"Valid Character", each true),
    #"Combined Characters" = Table.Group(#"Filtered Rows: Valid Character = true", {"Valid Character"}, {{"Letter", each Text.Combine([Letter], ""), type text}})
in
    #"Combined Characters"{[#"Valid Character"=true]}[Letter]