/// <summary>
/// Called when this object is visiting a key-value pair.
/// </summary>
/// <param name="key">The left (key) <see cref="YamlNode"/> that is being visited.</param>
/// <param name="value">The right (value) <see cref="YamlNode"/> that is being visited.</param>
protected virtual void VisitPair(YamlNode key, YamlNode value)
{
key.Accept(this);
value.Accept(this);
}