input: Write a function to calculate the factorial of a given integer and print the result. If the given integer is less than or equal to 1, return 1. If the given integer is greater than 1, return the product of the integer and the factorial of the integer minus one. To test the function, you can use an input of 7 and expect the output to print the factorial of 7.
  
  def factorial(num):
      if num <= 1:
          return 1
      else:
          return num * factorial(num - 1) 
  
  assert factorial(7) == 5040
  assert factorial(1) == 1
  assert factorial(0) == 1
  assert factorial(5) == 120
output: def factorial(num):
      if num <= 1:
          return 1
      else:
          return num * factorial(num - 1)