code: def expand_paths(inputs):
      
  
      seen = {}
  
      for dirname in inputs:
          dirname = normalize_path(dirname)
          if dirname in seen:
              continue
  
          seen[dirname] = 1
          if not os.path.isdir(dirname):
              continue
  
          files = os.listdir(dirname)
          yield dirname, files
  
          for name in files:
              if not name.endswith('.pth'):
                  # We only care about the .pth files
                  continue
              if name in ('easy-install.pth', 'setuptools.pth'):
                  # Ignore .pth files that we control
                  continue
  
              # Read the .pth file
              f = open(os.path.join(dirname, name))
              lines = list(yield_lines(f))
              f.close()
  
              # Yield existing non-dupe, non-import directory lines from it
              for line in lines:
                  if not line.startswith("import"):
                      line = normalize_path(line.rstrip())
                      if line not in seen:
                          seen[line] = 1
                          if not os.path.isdir(line):
                              continue
                          yield line, os.listdir(line)
docs: Yield sys.path directories that might contain "old-style" packages