Complete the function alternate_case in the t03_functions.py module. The module t03.py provides simple testing for this function.

Given a string parameter, this function returns a new string where all of the letters in the parameter string at an even index are converted to upper case and all of the letters at an odd index are converted to lower case. Non-letters are left alone. Some examples from executing t03.py:

alternate_case("abc")

AbC 

alternate_case("This is the 3rd sentence.")

ThIs iS ThE 3rD SeNtEnCe. 

Requirements

This function must:

Return, not print, the resulting strings