This method should only be invoked by the graph.scan.Elem instances.
This method should only be invoked by the graph.scan.Elem instances. It declares a scan output along
with the number of channels written to it.
Called by graph elements during their expansion, this method forwards a request
for input specifications to the UGenGraphBuilder.Context.
Called by graph elements during their expansion, this method forwards a request
for input specifications to the UGenGraphBuilder.Context. The context should
examine the input and return an appropriate value of type input.Value that
will then be stored under input.key in the acceptedInputs map of the builder
state.
Note that the builder will not check whether an entry with the key already exists in the map or not. It is the responsibility of the context to react appropriately to repeated calls with the same input key. For example, the same attribute key for a streaming operation may be used multiple times, perhaps with different streaming speeds.
If an input resource is not ready, the context should throw a MissingIn exception.
The builder will catch that exception and add the key to rejectedInputs instead
of acceptedInputs instead.