code: def is_leap(year):
      
      x = math.fmod(year, 4)
      y = math.fmod(year, 100)
      z = math.fmod(year, 400)
  
      # Divisible by 4 and,
      # either not divisible by 100 or divisible by 400.
      return not x and (y or not z)
docs: Leap year or not in the Gregorian calendar.