docs: def keys(self, namespace, prefix=None, limit=None, offset=None):
          """Get keys from a namespace"""
          params = [namespace]
          query = 'SELECT key FROM gauged_keys WHERE namespace = %s'
          if prefix is not None:
              query += ' AND key LIKE %s'
              params.append(prefix + '%')
          if limit is not None:
              query += ' LIMIT %s'
              params.append(limit)
          if offset is not None:
              query += ' OFFSET %s'
              params.append(offset)
          cursor = self.cursor
          cursor.execute(query, params)
          return [key for key, in cursor]