input: Write a python function to print the absolute paths of all directories and files in a given directory.
  assert print_paths(".") is None
output: import os
  
  def print_paths(directory):
      for root, dirs, files in os.walk(directory):
          for name in dirs:
              print(os.path.join(root, name))
          for name in files:
              print(os.path.join(root, name))