MutableExpander

Expander's label string.

True if the expander was created with expanded=True.

Remove the container and its contents entirely. A cleared container can't be reused.

Append a copy of another MutableExpander's children to this MutableExpander.

Change the expander's label and expanded state

Add a Markdown element to the container and return its index.

Add an Exception element to the container and return its index.