This is how I do stuff like this, and I very rarely have to use funny line-continuation characters:

    thisIsAnOutgoingBuffer = this_is_a_function(
      descriptiveKeywordArg=maxExchangeBufferLengthBytes,
      more_long_param=a_nested_function_call_with_long_params(
        inner_param=55,
        another_inner_param="Asdf"
      )
    )