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("3 4 + 2 * 7 /")==4
  assert evaluate("2 3 * 5 +")==11
  assert evaluate("10 2 8 * + 3 -")==23
  assert evaluate("4 6 / 1 + 2 *")==4
output: 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])