Function peek

fdbserver/VersionedBTree.actor.cpp:1340–1340

	}

	Future<Optional<T>> peek() { return peek_impl(this); }

	// Pop the next item on front of queue if it is <= inclusiveMaximum or if inclusiveMaximum is not present
	Future<Optional<T>> pop(Optional<T> inclusiveMaximum = {}) { return headReader.readNext(inclusiveMaximum); }