void ICollection.CopyTo(Array array, int index)
 {
     ReadOnlyDictionaryHelpers.CopyToNonGenericICollectionHelper <TValue>(_collection, array, index);
 }
 void ICollection.CopyTo(Array array, int index) => ReadOnlyDictionaryHelpers.CopyToNonGenericICollectionHelper <TKey>(m_collection, array, index);