code: def conv2d(x, W):
      """conv2d returns a 2d convolution layer with full stride."""
      return tf.nn.conv2d(x, W, strides=[1, 1, 1, 1], padding="SAME")
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import time
  import tensorflow
  from tensorflow.examples.tutorials.mnist import input_data
  import ray
  import ray.experimental.tf_utils
  from bigdl.dllib.utils.log4Error import invalidInputError
label_desc: Use image node_id 3 for calling a global function with example usage: conv2d(x, W) and returns: tf