static getCellResolution_(cellResolution) {
    if (!cellResolution) {
      return null;
    }
    const matches = /^(\d+) (\d+)$/.exec(cellResolution);

    if (!matches) {
      return null;
    }

    const columns = parseInt(matches[1], 10);
    const rows = parseInt(matches[2], 10);

    return {columns, rows};
  }
If ttp:cellResolution provided returns cell resolution info
with number of columns and rows into which the Root Container
Region area is divided

@param {?string} cellResolution
@return {?{columns: number, rows: number}}
@private