def is_prime_v1(integer):
    """Return 'True' if integer is a prime. Else 'False'."""
    if integer == 0:
        return False
    if integer == 1:
        return False  # 1 is a unit, not a prime
    for number in range(2, integer):
        if integer % number is 0:
            return False  # The number has a divisor other than itself and one.
    return True