input: Write a function to design a positive feedback loop for the provided Python program. The function should modify the original code to include a feedback mechanism that prints "You've got it!" after the loop completes successfully. If the input code is empty or incorrect, the function should return an empty string.
  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('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!")'
  assert positive_feedback_loop('') == ''
  assert positive_feedback_loop('for i in range(3): print("yo")') == 'for i in range(3):\n    print("yo")\n    i += 1\n    if i == 3:\n        print("You\'ve got it!")'
  assert positive_feedback_loop('invalid code') == ''
output: def positive_feedback_loop(code):
      if not code or 'for' not in code:
          return ''
      lines = code.split('\n')
      loop_line = lines[0]
      loop_var = loop_line.split(' ')[1].split(' in ')[0]
      loop_end = loop_line.split(' in ')[1].split(':')[0]
      feedback_code = f"{code}\n    {loop_var} += 1\n    if {loop_var} == {loop_end}:\n        print(\"You've got it!\")"
      return feedback_code