input: Write a function to evaluate a postfix expression. The input to the function should be a string with the postfix expression. The output should be the evaluated value of the expression.
  def evaluate(expression):
      expression = expression.split()
      stack = []
      for element in expression:
          if element.isdigit():
              stack.append(element)
          else:
              val1 = stack.pop()
              val2 = stack.pop()
              stack.append(str(eval(val2 + element + val1)))
      return (int(stack[0]))
  
  assert evaluate("2 3 + 4 5 * *") == 46
  assert evaluate("5 3 10 * +") == 35
  assert evaluate("7 2 / 3 *") == 10
  assert evaluate("2 3 + 4 5 * * 6 +") == 52
  assert evaluate("10 20 + 30 40 * +") == 1310
output: def evaluate(expression):
      expression = expression.split()
      stack = []
      for element in expression:
          if element.isdigit():
              stack.append(int(element))
          else:
              val1 = stack.pop()
              val2 = stack.pop()
              if element == '+':
                  stack.append(val2 + val1)
              elif element == '-':
                  stack.append(val2 - val1)
              elif element == '*':
                  stack.append(val2 * val1)
              elif element == '/':
                  stack.append(val2 // val1)
      return stack[0]