/// <summary>
/// Determines if current <see cref="PNCounterDictionary{TKey}"/> has a counter
/// registered under provided <paramref name="key"/>.
/// </summary>
public bool ContainsKey(TKey key) => _underlying.ContainsKey(key);
/// <summary>
/// Determines if current <see cref="PNCounterDictionary{TKey}"/> has a counter
/// registered under provided <paramref name="key"/>.
/// </summary>
public bool ContainsKey(TKey key) => _underlying.ContainsKey(key);