class Rocket:
    __slots__ = {
        'velocity': 'Speed relative to Earth in meters per second',
        'mass': 'Gross weight in kilograms',
    }
    @property
    def kinetic_energy(self):
        'Kinetic energy in Newtons'
        return self.mass * self.velocity ** 2

class Rocket(builtins.object)
 |  Readonly properties defined here:
 |
 |  kinetic_energy
 |      Kinetic energy in Newtons
 |
 |  ----------------------------------------------------------------------
 |  Data descriptors defined here:
 |
 |  mass
 |      Gross weight in kilograms
 |
 |  velocity
 |      Speed relative to Earth in meters per second

@dataclass(slots=True)
class Rocket:
    velocity: float = field(doc='Speed relative to Earth in meters per second')
    weight: float = field(doc='Gross weight in kilograms')