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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 get_variable_definitions(self, block_addr):
 """ Get variables that are defined at the specified block. :param int block_addr: Address of the block. :return: A set of variables. """


        if block_addr in self._outstates:
            return self._outstates[block_addr].variables
        return set()