class User:
        def __init__(self, username, email, profile):
            self.username = username
            self.email = email
            self.profile = profile
            self.coins = 0

    class Profile:
        def __init__(self, bio, pictures):
            self.bio = bio
            self.pictures = pictures


    class Image:
        def __init__(self, path, blurred=True):
            self.path = path
            self.blur = blurred

        def unblur():
            pass #TODO


    class Message:
        def __init__(self, contents, author):
            self.author = author
            self.contents = contents

        def unblur(self):
            assert type(self.contents) is Image, "Can't unblur a string"
            self.contents.unblur()


    class Chat:
        def __init__(self, seller, buyer):
            self.seller = seller
            self.buyer = buyer
            self.messages = list()

        def send_message(self, message):
            messages.append(message)
            pass #TODO


    class Seller(User):
        def __init__(self):
            self.name = name
            self.matches = list()
            self.available_buyers = list()

        def add_match(self, buyer):
            assert buyer in available_buyers
            matches.append(buyer)
            buyer.add_match(self)

        def add_buyer(self, buyer):
            available_buyers.append(buyer)


    class Buyer(User):
        def __init__(self):
            self.swipes = list()
            self.matches = list()

        def add_swipe(self, seller):
            swipes.append(seller)
            seller.add_buyer(self)

        def add_match(self, seller):
            assert seller in swipes
            matches.append(seller)

        def send_coins(self, num_coins, seller):
            assert seller in matches
            assert num_coins <= self.coins

            self.coins -= num_coins
            seller.coins += num_coins