input: Write a function to design a positive feedback loop for the given Python program. The function should modify the program to include a feedback mechanism that prints a positive message once the loop completes. If the given program is empty, return the input program without any changes.
  
  assert positive_feedback_loop("for i in range(10):\n    print(\"hello\")")=="for i in range(10):\n    print(\"hello\")\n    i += 1\n    if i == 10:\n        print(\"You've got it!\")"
  assert positive_feedback_loop("")==""
  assert positive_feedback_loop("for i in range(5):\n    print(\"hi\")")=="for i in range(5):\n    print(\"hi\")\n    i += 1\n    if i == 5:\n        print(\"You've got it!\")"
output: def positive_feedback_loop(program):
      if not program:
          return program
      lines = program.split('\n')
      loop_line = lines[0]
      loop_var = loop_line.split()[1].split('in')[0].strip()
      loop_range = int(loop_line.split('(')[1].split(')')[0])
      feedback_message = f"    {loop_var} += 1\n    if {loop_var} == {loop_range}:\n        print(\"You've got it!\")"
      return program + '\n' + feedback_message