docs: <T> DynamoDBTable getTable(Class<T> clazz) {
          DynamoDBTable table = clazz.getAnnotation(DynamoDBTable.class);
          if ( table == null )
              throw new DynamoDBMappingException("Class " + clazz + " must be annotated with " + DynamoDBTable.class);
          return table;
      }