code: public function setError($error)
      {
          if (!$this->_isNumericArray($error)) {
              $error = array($error);
          }
          $this->fields['Error']['FieldValue'] = $error;
          return $this;
      }
docs: Sets the value of the Error.
  
  @param mixed $error Error or an array of Error Error
  @return $this This instance