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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 build_extension_item(name: str, parameters: List[ExtensionParameter]) -> str: """ Build an extension definition. This is the reverse of :func:`parse_extension_item`. """

    return "; ".join(
        [name]
        + [
            # Quoted strings aren't necessary because values are always tokens.
            name if value is None else f"{name}={value}"
            for name, value in parameters
        ]
    )