Optional contextThe resulting action context.
Callback that returns a promise that resolves to the metadata about the stream.
This can contain things like the estimated number of total stream elements, or the order in which the bindings appear.
This callback can be invoked multiple times.
Each invocation can return a different metadata object,
if the previous one would have become invalidated (see metadata.state).
The actors that return this metadata will make sure that multiple calls properly cache this promise,
and that the cached object is properly invalidated if needed.
Metadata will not be collected until this callback is invoked.
This callback should resolve quickly, so it is safe to call and immediately await it.
The type of output.
Super interface for query operation results that represent some for of stream.
See
IQueryableResultBindings, IQueryableResultQuads