class Protobuf::Field::BytesField

def encode(value)
  value = value.serialize_to_string if value.is_a?(::Protobuf::Message)
  value.force_encoding(::Protobuf::Field::BytesField::BYTES_ENCODING) 
  string_size = ::Protobuf::Field::VarintField.encode(value.size)
  string_size << value
end