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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 from_parameter(cls: Type[XHXParameterType], parameter: str) -> Optional[XHXParameterType]: """ Return a XHXParameter instance from an index parameter :param parameter: Index parameter :return: """

        xhx = XHXParameter.re_xhx.match(parameter)
        if xhx:
            return cls(int(xhx.group(1)))

        return None