Description of which voice to use for a synthesis request.
Required. The language (and potentially also the region) of
the voice expressed as a
The name of the voice. If not set, the service will choose a
voice based on the other parameters such as language_code
The preferred gender of the voice. If not set, the service
will choose a voice based on the other parameters such as
language_code and name. Note that this is only a preference,
not requirement; if a voice of the appropriate gender is not
available, the synthesizer should substitute a voice with a
different gender rather than failing the request.