A map of tables and requests against those tables that were not processed. The UnprocessedItems value is in the same form as
            RequestItems, so you can provide this value directly to a subsequent BatchGetItem operation. For more information, see
            RequestItems in the Request Parameters section. Each UnprocessedItems entry consists of a table name and, for that table, a
            list of operations to perform (DeleteRequest or PutRequest). 
- DeleteRequest - Perform a DeleteItem
            operation on the specified item. The item to be deleted is identified by a Key subelement: - Key - A map of primary key attribute values that uniquely identify the item. Each entry in this map consists of an attribute name and an attribute value.
 
- PutRequest - Perform a PutItem operation on the specified item. The item to be put is identified by an
            Item subelement: - Item - A map of attributes and their values. Each entry in this map consists of an attribute name and an attribute value. Attribute values must not be null; string and binary type attributes must have lengths greater than zero; and set type attributes must not be empty. Requests that contain empty values will be rejected with a ValidationException. If you specify any attributes that are part of an index key, then the data types for those attributes must match those of the schema in the table's attribute definition.
 
Constraints:
 Declaration Syntax
 Declaration Syntax| C# | 
public Dictionary<string, List<WriteRequest>> UnprocessedItems { get; set; }