public IDocument CreateDocument(string path, string filename, string mimetype, byte[] contentBytes, string templateName = null)
{
     IDictionary<string, object> properties = new Dictionary<string, object>
     {
          [PropertyIds.Name] = filename,
          [PropertyIds.ObjectTypeId] = "lf:document"
     };

     // prepare properties
     if (!String.IsNullOrWhiteSpace(templateName))
     {
          List<String> secondaryTypes = new List<String>() { $"template:{templateName}", "lf:fields" };
          properties[PropertyIds.SecondaryObjectTypeIds] = secondaryTypes.ToArray();

          // example of setting fields
          properties["field:SOME_FIELD_NAME"] = "Some value";
     }

     IFolder parent = (IFolder)Session.GetObjectByPath(path);

     Stream stream = new MemoryStream(contentBytes);

     IContentStream contentStream = Session.ObjectFactory.CreateContentStream(filename, contentBytes.Length, mimetype, stream);

     // create the document
     return parent.CreateDocument(properties, contentStream, VersioningState.None);
}