Please Organise Which code goes into Functions and Which goes into T04

Add this function to the PyDev module functions.py. Test it from t04.py. The function must use a single stack to do its work. In a postfix expression, operators follow operands. Thus the infix expression: 125 is written as postfix expression: 125 which evaluates to 7. In postfix expressions as the operations are performed in the order that they appear. The expression: is equivalent to (4+5)1223 and evaluates to 102 . The algorithm for evaluation postfix expressions is: 1. Create a stack to store operands (i.e. values) 2. Walk through the expression string element by element: 1. If the element is a number, push it into the stack 3. When the expression is finished, the number on the top of the stack is the final answer. The stack should be empty after this number is popped. You do not have to do any error handling on poorly written postfix expressions. A valid postfix expression has at least one number in it