Which Python statement can be used to change case of all letters in s1? I.e. lower case letters will be upper case, and upper case letters will be lower case. For example, if s1 was "aB4-4eT", then s1...

Which Python statement can be used to change case of all letters in s1? I.e. lower case letters will be upper case, and upper case letters will be lower case.

For example, if s1 was "aB4-4eT", then s1 should be "Ab4-4Et".