'Returns 9 character Polish Identity Card Number,
Polish: Numer Dowodu Osobistego.
The card number consists of 3 letters followed by 6 digits (for example, ABA300000),
of which the first digit (at position 3) is the check digit.
https://en.wikipedia.org/wiki/Polish_identity_card'

@classmethod
def identity_card_number(cls):

    identity = []
    for _ in range(3):
        identity.append(cls.random_letter().upper())
    identity.append(0)
    for _ in range(5):
        identity.append(cls.random_digit())
    identity[3] = checksum_identity_card_number(identity)
    return u''.join((str(character) for character in identity))
