code: func ParseInt(b []byte) (int64, error) {
  	if v, ok, overflow := parseInt(b); !ok {
  		if overflow {
  			return 0, OverflowIntegerError
  		}
  		return 0, MalformedValueError
  	} else {
  		return v, nil
  	}
  }
docs: // ParseInt parses a Number ValueType into a Go int64