public sealed class DocumentPropertyInfo 

internal void KnowledgeGraphDocuments(KnowledgeGraph kg)
{
  // use the KnowledgeGraphPropertyInfo
  var propInfo = kg.GetPropertyNameInfo();
  var supportsDocs = propInfo.SupportsDocuments;
  var documentType = propInfo.DocumentTypeName;
  var hasDocumentType = propInfo.HasDocumentTypeName;   // available at Pro 3.6 only
  var documentInfo = propInfo.DocumentPropertyInfo;
}