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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def cross(self, vec):
 """Return the crossproduct between self and vec."""


        return Vec3(self.y * vec.z - self.z * vec.y,
                    self.z * vec.x - self.x * vec.z,
                    self.x * vec.y - self.y * vec.x)