#### buffered_stream::async_write_some

Start an asynchronous write. The data being written must be valid for the lifetime of the asynchronous operation.

    template<
        typename ConstBufferSequence,
        typename WriteHandler = default_completion_token_t<executor_type>>
    DEDUCED async_write_some(
        const ConstBufferSequence & buffers,
        WriteHandler && handler = default_completion_token_t< executor_type >());

###### Completion Signature

    void(asio::error_code, std::size_t)