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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 handle_unset_command(self, line: str, position: int, tokens: ParseResults) -> ParseResults: """Handle an ``UNSET X`` statement or raises an exception if it is not already set. :raises: MissingAnnotationKeyWarning """

        key = tokens['key']
        self.validate_unset_command(line, position, key)
        del self.annotations[key]
        return tokens