public static IFindFluent <TDocument> Find <TDocument>(this IMongoSet <TDocument> collection)
 {
     return(collection.Find(FilterDefinition <TDocument> .Empty));
 }
 public static IFindFluent <TDocument> Find <TDocument>(
     this IMongoSet <TDocument> collection,
     Expression <Func <TDocument, bool> > expression)
 {
     return(collection.Find(new ExpressionFilterDefinition <TDocument>(expression)));
 }