Assume you are given a stream of sequences. You need to implement a system similar to promises in JavaScript, where you wait for one stream to process before moving on to the next. For instance, consider how we watch movies on Netflix: the sequences come in order. Even if sequence 4 loads faster, it should still wait for sequences 1, 2, and 3 to load first. The goal is to ensure that the sequences are processed in the correct order, regardless of their loading times.