def is_leap_year(year):
    """
    Returns Boolean indicating if given year is a leap year.
    It is a leap year if the year is:
    * divisible by 4, but not divisible by 100
     OR
    * divisible by 400
    (Example of a "predicate function")

    Doctests:
    >>> is_leap_year(2001)
    False
    >>> is_leap_year(2020)
    True
    >>> is_leap_year(2000)
    True
    >>> is_leap_year(1900)
    False
    """
    return ((year % 4 == 0) and (year % 100 != 0)) or (year % 400 == 0)