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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 _convert(self, block_node):
 """ Convert a VEX block to an AIL block. :param block_node: A BlockNode instance. :return: An converted AIL block. :rtype: ailment.Block """


        if not type(block_node) is BlockNode:
            return block_node

        block = self.project.factory.block(block_node.addr, block_node.size)

        ail_block = ailment.IRSBConverter.convert(block.vex, self._ail_manager)
        return ail_block