input: def evaluate_postfix_expression(expression: str) -> int:
      """Evaluate a given postfix expression.
      >>> evaluate_postfix_expression("2 3 + 4 5 * *")
      46
      >>> evaluate_postfix_expression("7 2 + 4 * 5 /")
      8
      """
      tokens = expression.split()
      stack = []
      for token in tokens:
          if token.isdigit():
              stack.append(int(token))
          else:
              operand2 = stack.pop()
              operand1 = stack.pop()
              if token == '+':
                  stack.append(operand1 + operand2)
              elif token == '-':
                  stack.append(operand1 - operand2)
              elif token == '*':
                  stack.append(operand1 * operand2)
              elif token == '/':
                  stack.append(int(operand1 / operand2))
      return stack.pop()
output:     tokens = expression.split()
      stack = []
      for token in tokens:
          if token.isdigit():
              stack.append(int(token))
          else:
              operand2 = stack.pop()
              operand1 = stack.pop()
              if token == '+':
                  stack.append(operand1 + operand2)
              elif token == '-':
                  stack.append(operand1 - operand2)
              elif token == '*':
                  stack.append(operand1 * operand2)
              elif token == '/':
                  stack.append(int(operand1 / operand2))
      return stack.pop()