Method lower_bound

fdbserver/VersionedBTree.actor.cpp:5482–5482

		const_iterator upper_bound(const KeyRef& k) const { return mutations.upper_bound(k); }

		const_iterator lower_bound(const KeyRef& k) const { return mutations.lower_bound(k); }

		// erase [begin, end) from the mutation map
		void erase(const const_iterator& begin, const const_iterator& end) { mutations.erase(begin, end); }