def get_simple_singlesig(self) -> Optional['Descriptor']:
        """Returns innermost pk/pkh/wpkh descriptor, or None if we are not a simple singlesig.

        note: besides pk,pkh,sh(wpkh),wpkh, overly complicated stuff such as sh(pk),wsh(sh(pkh),etc is also accepted
        """
        if len(self.subdescriptors) == 1:
            return self.subdescriptors[0].get_simple_singlesig()
        return None
Returns innermost pk/pkh/wpkh descriptor, or None if we are not a simple singlesig.

        note: besides pk,pkh,sh(wpkh),wpkh, overly complicated stuff such as sh(pk),wsh(sh(pkh),etc is also accepted
        
electrum/descriptor.py