GROMACS

In order to dispatch work between Context instances, and to better implement functionality like looping, we should move to an observer pattern for data flow implementation details. This means that a Context will maintain knowledge of subscribers to the Futures it manages so that it can notify of data availability. Additionally, if a subscriber can consume multiple iterations of a Future (subgraph nodes in a while loop), it will be much easier to update the graph state and metadata (such as input figure prints).