code: def SUB(classical_reg, right):
      
      left, right = unpack_reg_val_pair(classical_reg, right)
      return ClassicalSub(left, right)
docs: Produce a SUB instruction.
  
      :param classical_reg: Left operand for the arithmetic operation. Also serves as the store target.
      :param right: Right operand for the arithmetic operation.
      :return: A ClassicalSub instance.