def non_parallel(self, vector):
        """Return True if vectors are non-parallel.

        Non-parallel vectors are vectors which are neither parallel
        nor perpendicular to each other.
        """
        if (self.is_parallel(vector) is not True and
                self.is_perpendicular(vector) is not True):
            return True
        return False
Return True if vectors are non-parallel.

        Non-parallel vectors are vectors which are neither parallel
        nor perpendicular to each other.