message: adding docu for Agent::IsValidAtTime
diff: @@ -130,6 +130,12 @@ bool Agent::AtGoal() const {
  return goal_definition_->AtGoal(*this);
  }
  +/**
  + * @brief checks validity of agent. feature is required with simulating datasets in closed loop.
  + *
  + * @param world_time ... current world time
  + * @return true if agent is valid
  + */
  bool Agent::IsValidAtTime(const float& world_time) const {
  return isgreaterequal(world_time + std::numeric_limits<float>::epsilon(),
  first_valid_timestamp_);
  