code: def create_tree(path, depth=DEPTH):
      
      os.mkdir(path)
      for i in range(NUM_FILES):
          filename = os.path.join(path, 'file{0:03}.txt'.format(i))
          with open(filename, 'wb') as f:
              f.write(b'foo')
      if depth <= 1:
          return
      for i in range(NUM_DIRS):
          dirname = os.path.join(path, 'dir{0:03}'.format(i))
          create_tree(dirname, depth - 1)
docs: Create a directory tree at path with given depth, and NUM_DIRS and
      NUM_FILES at each level.