Added Docstring for str_format1 method and created str_format2 method.
Added Docstring for str_format1 method and created str_format2 method.

UWPCE-PythonCert/IntroPython2016,weidnem/IntroPython2016,UWPCE-PythonCert/IntroPython2016,UWPCE-PythonCert/IntroPython2016,weidnem/IntroPython2016,Baumelbi/IntroPython2016,weidnem/IntroPython2016,Baumelbi/IntroPython2016