here is the code to produce the graph

graph_2 = tf.Graph()
with graph_2.as_default():
    a = tf.compat.v1.placeholder(tf.float32, name='input')
    b = a
    for i in range(5):
        b = tf.add(a, b)

writer = tf.compat.v1.summary.FileWriter('tbout/01_lab21', graph=graph_2)
writer.close()

then i start tensorboard with this
%tensorboard –logdir tboout/01_lab22

tensorboard produces a graph does not describe graph_2