SelectionContainerModifier constructor
      const
      SelectionContainerModifier({ 
    
- Key? key,
- Key? modifierKey,
- Widget? child,
- SelectionRegistrar? registrar,
- required SelectionContainerDelegate delegate,
Creates a selection container to collect the Selectables in the subtree.
If registrar is not provided, this selection container gets the
SelectionRegistrar from the context instead.
The delegate and child must not be null.
Implementation
const SelectionContainerModifier({
  super.key,
  super.modifierKey,
  super.child,
  this.registrar,
  required SelectionContainerDelegate this.delegate,
}) : assert(delegate != null);