code: def _hide_num_nodes(shape):
      """Set the first dimension as unknown"""
      shape = list(shape)
      shape[0] = None
      return shape
  
imports: import os
  import numpy
  import pickle
  import time
  import pgl.graph_kernel
  from collections import defaultdict
label_desc: Use image node_id 1 for calling a global function with example usage: _hide_num_nodes(shape) and returns: shape