code: function returns(func, validator, message) {
  	message = messageBuilder(message || 'vet/utils/returns error!');
  
  	return function _returnsInstance() {
  		var args = arguments;
  		var result = func.apply(this, arguments);
  
  		if (validator(result)) {
  			return result;
  		} else {
  			throw new Error(message.call(this, result));
  		}
  	};
  }
docs: Wraps a function in a validator which checks its return value, and throws an error if the return value is bad.
  
  @param func - the function to wrap
  @param validator - the validator function.  This gets passed the return value
  @param message - an optional message string to pass into the error thrown
  @returns a wrapped function that throws an error if the return value doed not pass validation
  @memberof vet.utils