code: def half_plus_two():
      a = tf.get_variable("a", shape=[])
      b = tf.get_variable("b", shape=[])
      x = tf.placeholder(tf.float32)
      y = a * x + b
      hub.add_signature(inputs=x, outputs=y)
  
imports: import tensorflow.compat.v1
  import tensorflow_hub
label_desc: Use image node_id 1 for calling a global function with example usage: half_plus_two() without return types