/// <summary>Add a relationship between two NPCs.</summary>
/// <param name="left">The left NPC.</param>
/// <param name="leftType">The left relationship type (i.e. <paramref name="left"/> is the _____ of <paramref name="right"/>).</param>
/// <param name="right">The right NPC.</param>
/// <param name="rightType">The right relationship type (i.e. <paramref name="right"/> is the _____ of <paramref name="left"/>).</param>
private void AddRelationship(CharacterInfo left, Relationship leftType, CharacterInfo right, Relationship rightType)
{
left.AddRelationship(rightType, right);
right.AddRelationship(leftType, left);
}