The InnerAssistant interface is a marker interface intended to indicate that
a given LayoutAssistant implementation represents a LayoutManager which
is Container specific. Container specific LayoutManager implementations are
usually implemented as an inner class of the Container type to which they
are intended (e.g. JRootPane$1 as found in javax.swing.JRootPane).
InnerAssistant implementations would typically be filtered out of any list
offered to the user when selecting a LayoutManager (e.g. from a
PropertyEditor offered in a PropertyInspector when editing the layout
property of a Container).