FileNameUnset

This error means that you tried to save a Node, but initialized it with raw data and never set a filename. To fix this, see Changing the active file.

Here's an example:

x = Node()
x.get('test')
# or
x.test

Output: <RootNode>.test does not exist

The error message will always write the text <RootNode> since the method returning will not be able to determine what you have named the variable containing the Node object. For more information, see Terminology.