<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 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)