String label

If non-null, sets the "label" semantic to the given value.

Source 

String get label => _label;
void label=(String value)

Source 

set label(String value) {
  if (label == value)
    return;
  bool hadValue = label != null;
  _label = value;
  markNeedsSemanticsUpdate(onlyChanges: (value != null) == hadValue);
}