$*$ Write a function $`$vigenere$\_$decrypt$`$ using the following template. The $`$method$`$ keyword argument allows the user to specify whether they wish to use the Kasiski method or the Index of Coincidence method to find the key length. If no method is specified, the Kasiski method is used by default.

$```$

def vigenere$\_$decrypt$($Y$,$ key$\_$start$=7,$ key$\_$end$=12,$ method$=$"kasiski"$)$:

Y $=$ only$\_$letters$($Y$,$ case$=$"upper"$)$ # Remove spaces

if method $==$ "kasiski":

key$\_$length$\_$fn $=$ key$\_$length$\_$kasiski

elif method $==$ "coincidence":

key$\_$length$\_$fn $=$ key$\_$length$\_$coincidence

else:

raise ValueError$(\text{'}\text{'}\text{'}$key$\_$length should be either "kasiski" or "coincidence"$\text{'}\text{'}\text{'})$

k $=$ key$\_$length$\_$fn$($Y$,$ key$\_$start$=$key$\_$start, key$\_$end$=$key$\_$end$)$ # $`$k$`$ is the predicted key length

shifts $=???$ # The predicted shift amounts

X $=???$ # The predicted plaintext. Use your $`$vigenere$`$ function from high above

return X$.$lower$()$

$```$

$*$ Try to decrypt the above ciphertext from Section $5\mathrm{.}2$ of the textbook.

$```$

Y $=\text{'}\text{'}\text{'}$zpgdl rjlaj kpylx zpyyg lrjgd lrzhz qyjzq repvm swrzy rigzh

zvreg kwivs saolt nliuw oldie aqewf iiykh bjowr hdogc qhkwa

jyagg emisr zqoqh oavlk bjofr ylvps rtgiu avmsw lzgms evwpc

dmjsv jqbrn klpcf iowhv kxjbj pmfkr qthtk ozrgq ihbmq sbivd

ardym qmpbu nivxm tzwqv gefjh ucbor vwpcd xuwft qmoow jipds

fluqm oeavl jgqea lrkti wvext vkrrg xani'$\text{'}\text{'}$

vigenere$\_$decrypt$($Y$)$

$```$

$*$ Select one of your classmate's Vigen$$re ciphertexts that were posted on Canvas Discussion and attempt to decrypt it using your $`$vigenere$\_$decrypt$`$ function. Assign the ciphertext to the variable name $`$Y$`($use triple quotation marks to allow line breaks$).$ Try using both key length methods.

$```$

vigenere$\_$decrypt$($Y$,$ method$=$"kasiski"$)$

$```$

and

$```$

vigenere$\_$decrypt$($Y$,$ method$=$"coincidence"$)$

$```$

Do they both wok?