void DiscreteTrajectory<Frame>::WriteSubTreeToMessage(
not_null<serialization::Trajectory*> const message,
std::vector<DiscreteTrajectory<Frame>*>& forks) const {
Forkable<DiscreteTrajectory, Iterator>::WriteSubTreeToMessage(message, forks);
for (auto const& pair : timeline_) {
Instant const& instant = pair.first;
DegreesOfFreedom<Frame> const& degrees_of_freedom = pair.second;
auto const instantaneous_degrees_of_freedom = message->add_timeline();
instant.WriteToMessage(instantaneous_degrees_of_freedom->mutable_instant());
degrees_of_freedom.WriteToMessage(
instantaneous_degrees_of_freedom->mutable_degrees_of_freedom());
}
}
