code: def _fetch_data(self):
          
          self._view_col0 = clamp(self._view_col0, 0, self._max_col0)
          self._view_row0 = clamp(self._view_row0, 0, self._max_row0)
          self._view_ncols = clamp(self._view_ncols, 0,
                                   self._conn.frame_ncols - self._view_col0)
          self._view_nrows = clamp(self._view_nrows, 0,
                                   self._conn.frame_nrows - self._view_row0)
          self._conn.fetch_data(
              self._view_row0,
              self._view_row0 + self._view_nrows,
              self._view_col0,
              self._view_col0 + self._view_ncols)
docs: Retrieve frame data within the current view window.
  
          This method will adjust the view window if it goes out-of-bounds.