input: def understand_recursion():
      """This function is designed to illustrate the concept of recursion in Python.
      It defines a recursive function to calculate the factorial of a number.
      >>> understand_recursion()
      Factorial of 5 is 120
      """
      def factorial(n):
         if n == 1:
            return 1
         else:
            return n * factorial(n - 1)
  
      result = factorial(5)
      print("Factorial of 5 is ", result)
output:     understand_recursion()