input: Write a function to display a directory tree structure with indentation.
  assert make_tree('/home/myUser/testFolder') == None
  assert make_tree('/home/myUser/anotherFolder') == None
output: import os
  
  def make_tree(path, indent=0):
      if not os.path.isdir(path):
          return None
      files_and_dirs = sorted(os.listdir(path))
      for item in files_and_dirs:
          item_path = os.path.join(path, item)
          print(' ' * indent + item)
          if os.path.isdir(item_path):
              make_tree(item_path, indent + 2)