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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _render(item: ConfigItem, indent: str = "") -> str: """ Render a single config item, with the provided indent """

    optional = item.default_value != _NO_DEFAULT

    if is_configurable(item.annotation):
        rendered_annotation = f"{item.annotation} (configurable)"
    else:
        rendered_annotation = str(item.annotation)

    rendered_item = "".join([
            # rendered_comment,
            indent,
            "// " if optional else "",
            f'"{item.name}": ',
            rendered_annotation,
            f" (default: {item.default_value} )" if optional else "",
            f" // {item.comment}" if item.comment else "",
            "\n"
    ])

    return rendered_item