
            <li>targets: Has the targets (e.g hmaps/pafs) created in convert_locs_to_targets
            <li>pred: Has the output of network created in define_network. It'll be a list if networks output was a list.
        </ul>
        Outputs<br>
        <ul>
            <li>loss: The loss function to be optimized.
        </ul>
        <p>Override this function to define your own loss function.</p>
        <pre><code>
          def loss(self,targets, pred):
              hmap_loss = tf.sqrt(tf.nn.l2_los