type FlexRenderProps<TFeatures, TData, TValue> =
  | {
  cell: Cell<TFeatures, TData, TValue>;
  footer?: never;
  header?: never;
}
  | {
  cell?: never;
  footer?: never;
  header: Header<TFeatures, TData, TValue>;
}
  | {
  cell?: never;
  footer: Header<TFeatures, TData, TValue>;
  header?: never;
};