-xca = polybius_decipher(sca, keyword='a', column_order=col_a, row_order=row_a,
- column_first=col_first_a, wrap_alphabet=wrap_a)
-xca
+pa = polybius_decipher(sca, keyword='a', column_order=col_a, row_order=row_a,
+ column_first=col_first_a, wrap_alphabet=wrap_a,
+ letters_to_merge={'z': 'y'})
+pa