Course 2 Week 3 Exercise one_hot_matrix function declaring C as a tf.constant

Why do we need to specify C as a tf.constant within the function if it is already being called into the function as a constant? I do not understand the " C = tf.constant(C, name = ‘C’)" step and why is the same not done for labels?

I don’t see any C as tf.constant in one hot matrix function? Can you please post the code you have a question about?