allowing space in encoding function (Sage ShiftCryptosystem)

I am using sage to implement an encryption function that takes in plain text and converts it a cipher text ignoring space and non alphabetic characters(including them i开发者_StackOverflow中文版n encoded text). the encoding function however, removes all spaces and ignores non alphabetic characters(not including them in encoded text). I could not find any documentation on the function. Any help?

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Is this what you are looking for? The examples make it pretty clear that this is what is intended.

Sage documentation on the ShiftCryptoSystem

Also, note that

sage: ShiftCryptosystem?

will take you the same place in the command line or notebook interface. Double question marks start getting you source code, hopefully that will lead you somewhere. Keep in mind that these cryptosystems are intended for pedagogical use.