def METHOD_NAME(self, positions):
    initial_velocities = []
    for x in positions:
        initial_velocities.append(
            np.real(
                (-1j * self.omega * self.mode_param)
                * self._compute_nonparametrized_mode(
                    self.base_length * x, self.base_length, self.beta
                )
            )
        )
    return np.array(initial_velocities)