ent members.  Compound
    elements are lists and list-like constructs.

    All transition methods are disabled (redefined as `invalid_input`).
    Override individual methods in subclasses to re-enable.

    For example, once an initial bullet list item, say, is recognized, the
    `BulletList` subclass takes over, with a "bullet_list" node as its
    container.  Upon encountering the initial bullet list item, `Body.bullet`
    calls its ``self.nested_list_parse`` (`RSTState.nested_list_parse`), which
    starts up a nested parsing session with `BulletList` as the initial state.
    Only the ``bullet`` transition method is enabled in `BulletList`; as long
    as only bullet list items are encountered, they are parsed and inserted
    into the container.  The first construct which is *not* a bullet list item
    triggers the `invalid_input` method, which ends the nested parse and
    closes the container.  `BulletList` needs to recognize input that is
    invalid in the context of a bullet list, which means everything *other
    than* bullet list items, so it inherits the transition list created in
    `Body`.
    Nc