public function only($fields)
    {
        $this->only = array_merge($this->only, is_array($fields) ? $fields : func_get_args());

        return $this;
    }
public function only($fields)
    {
        $this->only = array_merge($this->only, is_array($fields) ? $fields : func_get_args());

        return $this;
    }
public function only ( $ fields ) { $ this -> only = array_merge ( $ this -> only , is_array ( $ fields ) ? $ fields : func_get_args ( ) ) ; return $ this ; }
Filter fields to output using sparse fieldsets.

@param  string[]|string $fields
@return $this
Filter fields to output using sparse fieldsets .