Generic API for an oplet that processes streaming data on 0-N input ports
and produces 0-M output streams on its output ports. An input port may be
connected with any number of streams from other oplets. An output port may
connected to any number of input ports on other oplets.
Get the input stream data handlers for this oplet. The number of handlers
must equal the number of configured input ports. Each tuple
arriving on an input port will be sent to the stream handler for that