code: def _normalize_stmt_idx(self, block_addr, stmt_idx):
          
  
          if type(stmt_idx) is int:
              return stmt_idx
  
          if stmt_idx == DEFAULT_STATEMENT:
              vex_block = self.project.factory.block(block_addr).vex
              return len(vex_block.statements)
  
          raise AngrBackwardSlicingError('Unsupported statement ID "%s"' % stmt_idx)
docs: For each statement ID, convert 'default' to (last_stmt_idx+1)
  
          :param block_addr:  The block address.
          :param stmt_idx:    Statement ID.
          :returns:           New statement ID.