get
Gets data.
This gets data previously stored with StorageTable.insert.
key is the key used to identify the data.
partitionId secondary key. If partitioning is supported (see StorageTableSpec.supportExpiration), it must be non-null. If partitioning is not supported it must be null.
Returns the stored data or null
if there is no data for the given key (including the case when the record has expired).