Do not use tf.reset_default_graph() to clear nested graphs

This error message is displayed when you call tf.reset_default_graph() in one of the following scenarios:

• Inside a with graph.as_default(): block.
• Inside a with tf.Session(): block.
• Between creating a tf.InteractiveSession and calling sess.close().

Each of these scenarios involves registering a default (and potentially "nested") tf.Graph object, which will be unregistered when you exit the block (or close the tf.InteractiveSession). Resetting the default graph in those scenarios would leave the system in an inconsistent state, so you should ensure to exit the block (or close the tf.InteractiveSession) before calling tf.reset_default_graph().