code: def get_operand_expr(self, operand, mode="post"):
          
          if isinstance(operand, ReilRegisterOperand):
              if operand.name in self._arch_info.registers_all:
                  # Process architectural registers (eax, ebx, etc.)
                  expr = self.get_register_expr(operand.name, mode=mode)
              else:
                  # Process temporal registers (t0, t1, etc.)
                  var_name = self._get_var_name(operand.name, mode)
                  expr = self._translator.make_bitvec(operand.size, var_name)
          elif isinstance(operand, ReilImmediateOperand):
              expr = smtsymbol.Constant(operand.size, operand.immediate)
          else:
              raise Exception("Invalid operand: %s" % str(operand))
  
          return expr
docs: Return a smt bit vector that represents a register (architectural or
          temporal).