guard clauses: bad example

is_platypus.py

# Sorry for the silly example
def is_platypus(self):
    if self.is_mammal():
        if self.has_fur():
            if self.has_beak():
                if self.has_tail():
                    if self.can_swim():
                        # It's a platypus!
                        return True
    # Not a platypus
    return False