code: function(err, results) {
    if(err) {
      this.success = false;
      this.error = err;
      this.results = null;
  
      // customize error for error types
      if(util.isError(err)) {
        this.error = {
          message: err.message,
          type: err.type,
          arguments: err.arguments
        };
        if(NODE_ENV === 'development') {
          this.error.stack = err.stack;
        }
      }    
  
    } else {
      this.success = true;
      this.error = null;      
      this.results = convertToClient(results);    
    }
  }
docs: Creates a uniform Json response object
  @param err the optional error
  @param results the optional results
  @constructor