Added Api.ai session_id as optional parameter

reference/library-reference.rst

@@ -221,7 +221,7 @@ Returns the most likely transcription if ``show_all`` is false (the default). Ot
 
 Raises a ``speech_recognition.UnknownValueError`` exception if the speech is unintelligible. Raises a ``speech_recognition.RequestError`` exception if the speech recognition operation failed, if the key isn't valid, or if there is no internet connection.
 
-``recognizer_instance.recognize_api(audio_data, client_access_token, language = "en", show_all = False)``
+``recognizer_instance.recognize_api(audio_data, client_access_token, language = "en", session_id=None, show_all = False)``
 ----------------------------------------------------------------------------------------
 
 Perform speech recognition on ``audio_data`` (an ``AudioData`` instance), using the api.ai Speech to Text API.
@@ -230,6 +230,8 @@ The api.ai API client access token is specified by ``client_access_token``. Unfo
 
 Although the recognition language is specified when creating the api.ai agent in the web console, it must also be provided in the ``language`` parameter as an RFC5646 language tag like ``"en"`` (US English) or ``"fr"`` (International French), defaulting to US English. A list of supported language values can be found in the `API documentation <https://api.ai/docs/reference/#languages>`__.
 
+The session_id is a string token up to 36 symbols long, used to identify the client and to manage sessions parameters (including contexts) per client.
+
 Returns the most likely transcription if ``show_all`` is false (the default). Otherwise, returns the `raw API response <https://api.ai/docs/reference/#a-namepost-multipost-query-multipart>`__ as a JSON dictionary.
 
 Raises a ``speech_recognition.UnknownValueError`` exception if the speech is unintelligible. Raises a ``speech_recognition.RequestError`` exception if the speech recognition operation failed, if the key isn't valid, or if there is no internet connection.
@@ -307,4 +309,4 @@ If ``convert_rate`` is specified and the audio sample rate is not ``convert_rate
 
 If ``convert_width`` is specified and the audio samples are not ``convert_width`` bytes each, the resulting audio is converted to match.
 
-Writing these bytes directly to a file results in a valid `FLAC file <https://en.wikipedia.org/wiki/FLAC>`__.
+Writing these bytes directly to a file results in a valid `FLAC file <https://en.wikipedia.org/wiki/FLAC>`__.