@staticmethod
def is_leap(year):
    """
        Checking if year is leap.

        :param year: year
        :type year: int

        :return: result of checking
        :rtype: bool
        """
    if isinstance(year, int):
        return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)
    raise ValueError('Year must be integer.')
