code: func (ec *Client) HeaderByHash(ctx context.Context, hash common.Hash) (*types.Header, error) {
  	var head *types.Header
  	err := ec.c.CallContext(ctx, &head, "eth_getBlockByHash", hash, false)
  	if err == nil && head == nil {
  		err = ethereum.NotFound
  	}
  	return head, err
  }
docs: // HeaderByHash returns the block header with the given hash.