Pretty-print a config in sort-of-JSON+comments.

def render_config(config: Config, indent: str = "") -> str:
    """
    Pretty-print a config in sort-of-JSON+comments.
    """
    # Add four spaces to the indent.
    new_indent = indent + "    "

    return "".join([
            # opening brace + newline
            "{\n",
            # "type": "...", (if present)
            f'{new_indent}"type": "{config.typ3}",\n' if config.typ3 else '',
            # render each item
            "".join(_render(item, new_indent) for item in config.items),
            # indent and close the brace
            indent,
            "}\n"
    ])