code: function krillPrimGetKey(pred)
  {
  	var key, keysFound = 0;
  
  	for (var val in pred) {
  		keysFound++;
  		key = val;
  	}
  
  	if (keysFound > 1)
  		throw (new VError('predicate "%j": expected one key, ' +
  		    'but found %d', pred, keysFound));
  
  	if (keysFound < 1)
  		throw (new VError('predicate "%j": missing key', pred));
  
  	return (key);
  }
docs: /*
  Gets the key for the given predicate.  This is the operator at the root of
  this predicate ("lt" for less-than, "and" for boolean "and", and so on).
  
  Input:
  - pred: The predicate to get the key for
  Output:
  - returns the key for the specified predicate object