code: def filter_req_paths(paths, func):
      
      if not isinstance(paths, list):
          raise ValueError("Paths must be a list of paths.")
  
      libs = set()
      junk = set(['\n'])
      for p in paths:
          with p.open(mode='r') as reqs:
              lines = set([line for line in reqs if func(line)])
              libs.update(lines)
  
      return list(libs - junk)
docs: Return list of filtered libs.