code: def _nth_str(n):
      
      if n % 10 == 1 and n % 100 != 11:
          return "%dst" % n
      if n % 10 == 2 and n % 100 != 12:
          return "%dnd" % n
      if n % 10 == 3 and n % 100 != 13:
          return "%drd" % n
      return "%dth" % n
docs: Return posessive form of numeral `n`: 1st, 2nd, 3rd, etc.