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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 sharepoint(self, *, resource=''):
 """ Get an instance to read information from Sharepoint sites for the specified account resource :param str resource: Custom resource to be used in this sharepoint object (Defaults to parent main_resource) :return: a representation of Sharepoint Sites :rtype: Sharepoint :raises RuntimeError: if protocol doesn't support the feature """


        if not isinstance(self.protocol, MSGraphProtocol):
            # TODO: Custom protocol accessing OneDrive/Sharepoint Api fails here
            raise RuntimeError(
                'Sharepoint api only works on Microsoft Graph API')

        return Sharepoint(parent=self, main_resource=resource)