input: def evaluate_postfix_expression(expression: str) -> int:
      """Evaluates a given postfix expression.
      
      >>> evaluate_postfix_expression("2 3 + 4 5 * *")
      46
      >>> evaluate_postfix_expression("10 4 3 + 2 * -")
      -4
      """
      stack = []
      for token in expression.split():
          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(operand1 / operand2)
      return stack[0]
output:     stack = []
      for token in expression.split():
          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(operand1 / operand2)
      return stack[0]