public function postField($column, $value = null)
    {
        // If the column is an array, we will assume it is an array of key-value pairs
        // and can add them each as a post field.
        if (is_array($column)) {
            return $this->postFieldNested(function ($query) use ($column) {
                foreach ($column as $key => $value) {
                    $query->postField($key, $value);
                }
            });
        }

        $this->body[] = compact('column', 'value');

        return $this;
    }