code: func (bi *BigInt) SetString(x string, base int) {
  	bi.bigint.SetString(x, base)
  }
docs: // SetString sets the big int to x.
  //
  // The string prefix determines the actual conversion base. A prefix of "0x" or
  // "0X" selects base 16; the "0" prefix selects base 8, and a "0b" or "0B" prefix
  // selects base 2. Otherwise the selected base is 10.