code: def get_existing_path(path, topmost_path=None):
      
      prev_path = None
  
      if topmost_path:
          topmost_path = os.path.normpath(topmost_path)
  
      while True:
          if os.path.exists(path):
              return path
  
          path = os.path.dirname(path)
          if path == prev_path:
              return None
  
          if topmost_path and os.path.normpath(path) == topmost_path:
              return None
  
          prev_path = path
docs: Get the longest parent path in `path` that exists.
  
      If `path` exists, it is returned.
  
      Args:
          path (str): Path to test
          topmost_path (str): Do not test this path or above
  
      Returns:
          str: Existing path, or None if no path was found.