error in Harris features in image processing?

Hi, I have watched this video https://www.youtube.com/watch?v=ddXvs1Wp95A in you tube . and I followed all the codes that he described for detecting object but one part,describing rectangle, (because this line was long and not readable in video) was not readable for me .I know it may seem easy but my profession field is architecture and I am absolutely beginner in this field so If it is possible I ask for the code in (line 16 in the function findtemplate) which is about describing a rectangular.I mean I do not know how to fix error in line 16

Thank you so much