code: func EncodeBig(bigint *big.Int) string {
  	nbits := bigint.BitLen()
  	if nbits == 0 {
  		return "0x0"
  	}
  	return fmt.Sprintf("%#x", bigint)
  }
docs: // EncodeBig encodes bigint as a hex string with 0x prefix.
  // The sign of the integer is ignored.