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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 control(self) -> Optional[HTMLElement]: """Return related HTMLElement object."""

        id = self.getAttribute('for')
        if id:
            if self.ownerDocument:
                return self.ownerDocument.getElementById(id)
            elif isinstance(id, str):
                from wdom.document import getElementById
                return getElementById(id)
            else:
                raise TypeError('"for" attribute must be string')
        return None