Utility class for working with channels in the Pregel system. Provides static methods for subscribing to channels and writing to them.
Channels are the communication pathways between nodes in a Pregel graph. They enable message passing and state updates between different parts of the graph.
class ChannelCreates a PregelNode that subscribes to a single channel. This is used to define how nodes receive input from channels.
Creates a ChannelWrite that specifies how to write values to channels. This is used to define how nodes send output to channels.