def encode_string(string)
      raise ArgumentError, "String must be present" if !string
      encode_varint(string.bytesize) + BTC::Data.ensure_binary_encoding(string)
    end
def encode_string(string)
      raise ArgumentError, "String must be present" if !string
      encode_varint(string.bytesize) + BTC::Data.ensure_binary_encoding(string)
    end
Returns the binary representation of the var-length string.