Document representing the expected state of data in DynamoDB.
            Note: setting both Expected and ExpectedState is not supported and
            will result in an exception being thrown.
            
            For the operation to succeed, the data in DynamoDB must be equal
            to the attributes in Expected. If an attribute in Expected
            is set to null, that attribute must not be preset on the item in DynamoDB.
            
 Declaration Syntax
 Declaration Syntax| C# | 
public Document Expected { get; set; }