public virtual IEnumerable <ForeignKey> FindForeignKeys([NotNull] IReadOnlyList <IProperty> properties)
{
Check.HasNoNulls(properties, nameof(properties));
Check.NotEmpty(properties, nameof(properties));
var declaredForeignKeys = FindDeclaredForeignKeys(properties);
return(BaseType == null
? declaredForeignKeys
: declaredForeignKeys.Concat(BaseType.FindForeignKeys(properties)));
}