How to use the ailment.Stmt function in ailment

def observe(self, ins_addr, stmt, block, state, ob_type):
        if self._observation_points is not None and (ins_addr, ob_type) in self._observation_points:
            if isinstance(stmt, pyvex.IRStmt.IRStmt):
                # it's an angr block
                vex_block = block.vex
                # OP_BEFORE: stmt has to be IMark
                if ob_type == OP_BEFORE and type(stmt) is pyvex.IRStmt.IMark:
                    self.observed_results[(ins_addr, ob_type)] = state.copy()
                # OP_AFTER: stmt has to be last stmt of block or next stmt has to be IMark
                elif ob_type == OP_AFTER:
                    idx = vex_block.statements.index(stmt)
                    if idx == len(vex_block.statements) - 1 or type(
                            vex_block.statements[idx + 1]) is pyvex.IRStmt.IMark:
                        self.observed_results[(ins_addr, ob_type)] = state.copy()
            elif isinstance(stmt, ailment.Stmt.Statement):
                # it's an AIL block
                self.observed_results[(ins_addr, ob_type)] = state.copy()