input: Write a function to modify the given Python program to print 'Happy Holidays' 10 times instead of 'Hello World'. Return the modified code as a string.
  assert modify_greeting("for i in range(10):\n    print('Hello World')") == "for i in range(10):\n    print('Happy Holidays')"
  assert modify_greeting("") == ""
  assert modify_greeting("for i in range(5):\n    print('Hello')") == "for i in range(5):\n    print('Happy Holidays')"
  assert modify_greeting("print('Hello World')") == "print('Happy Holidays')"
output: def modify_greeting(code):
      return code.replace("Hello World", "Happy Holidays")