code: def get_block(self, namespace, offset, key):
          
          cursor = self.cursor
          cursor.execute('SELECT data, flags FROM gauged_data '
                         'WHERE namespace = %s AND "offset" = %s AND key = %s',
                         (namespace, offset, key))
          row = cursor.fetchone()
          return (None, None) if row is None else row
docs: Get the block identified by namespace, offset, key and
          value