clearSelection method
Clear the current selection.
When restoreInitialSelection is true, the dropdown returns to the
initial selection it started with (if any). When it is false, the
dropdown is cleared completely and the hint/header placeholder is shown.
This works whether the overlay is currently open or closed.
Implementation
void clearSelection({bool restoreInitialSelection = true}) {
_state?._clearSelection(
restoreInitialSelection: restoreInitialSelection,
);
}