def possible_links(source_node, sink_node):
 possible = []
 for source in source_node.output_channels():
  for sink in sink_node.input_channels():
   if compatible_channels(source, sink):
    possible.append((source, sink))
 return possible

def possible_links ( source_node , sink_node ) : possible = [ ] for source in source_node . output_channels ( ) : for sink in sink_node . input_channels ( ) : if compatible_channels ( source , sink ) : possible . append ( ( source , sink ) ) return possible
return a list of tuples .