Include a statement in the final slice.

        :param int block_address:   Address of the basic block.
        :param int stmt_idx:        Statement ID.

def _pick_statement(self, block_address, stmt_idx):
        """
        Include a statement in the final slice.

        :param int block_address:   Address of the basic block.
        :param int stmt_idx:        Statement ID.
        """

        # TODO: Support context-sensitivity

        # Sanity check
        if not isinstance(block_address, int):
            raise AngrBackwardSlicingError("Invalid block address %s." % block_address)
        if not isinstance(stmt_idx, int):
            raise AngrBackwardSlicingError("Invalid statement ID %s." % stmt_idx)

        self.chosen_statements[block_address].add(stmt_idx)