code: function printWarning(context, kind, err)
  {
  	if (context !== null) {
  		console.error('warn: %s: %s', context.label(), err.message);
  	} else {
  		console.error('warn: %s', err.message);
  	}
  }
docs: /*
  The signature for this function is defined in node-vstream.  The point is to
  provide enough context to report which object this was at each stage in the
  pipeline, like "JSON object #52 from line #57".