Python 3 Coding:

Unset_location(puzzle, loc): given a puzzle and a location (row, col), try to remove the value at that location (change to None) Return True if the puzzle was successfully changed (the value at that location is removed). Return False if the location is not valid, or there is currently no value at that location. given a puzzle, return its size as an integer. You do not need to check whether the given puzzle is valid. given a positive size, return a list of the numbers which can be validly placed in a puzzle of that size. check if a puzzle contains only valid numbers. If the puzzle is incomplete, also allow None in the puzzle, complete will be a boolean indicating whether or not the puzzle is complete. You do not need to check that the puzzle is valid, only if the numbers used are correct. given a list of numbers xs and a number n, check whether xs has repeated values of n. Return True if v occurs more than once in xs; return False otherwise. You may not use count()! return the row at the specified row_index from puzzle as a list Return None if the row_index is invalid