def list_voices(self, language_code=None, retry=google.api_core.gapic_v1.method.DEFAULT, timeout=google.api_core.gapic_v1.method.DEFAULT, metadata=None):
    '\n        Returns a list of ``Voice`` supported for synthesis.\n\n        Example:\n            >>> from google.cloud import texttospeech_v1beta1\n            >>>\n            >>> client = texttospeech_v1beta1.TextToSpeechClient()\n            >>>\n            >>> response = client.list_voices()\n\n        Args:\n            language_code (str): Optional (but recommended)\n                `BCP-47 <https://www.rfc-editor.org/rfc/bcp/bcp47.txt>`__ language tag.\n                If specified, the ListVoices call will only return voices that can be\n                used to synthesize this language\\_code. E.g. when specifying "en-NZ",\n                you will get supported "en-*" voices; when specifying "no", you will get\n                supported "no-*" (Norwegian) and "nb-*" (Norwegian Bokmal) voices;\n                specifying "zh" will also get supported "cmn-*" voices; specifying\n                "zh-hk" will also get supported "yue-\\*" voices.\n            retry (Optional[google.api_core.retry.Retry]):  A retry object used\n                to retry requests. If ``None`` is specified, requests will not\n                be retried.\n            timeout (Optional[float]): The amount of time, in seconds, to wait\n                for the request to complete. Note that if ``retry`` is\n                specified, the timeout applies to each individual attempt.\n            metadata (Optional[Sequence[Tuple[str, str]]]): Additional metadata\n                that is provided to the method.\n\n        Returns:\n            A :class:`~google.cloud.texttospeech_v1beta1.types.ListVoicesResponse` instance.\n\n        Raises:\n            google.api_core.exceptions.GoogleAPICallError: If the request\n                    failed for any reason.\n            google.api_core.exceptions.RetryError: If the request failed due\n                    to a retryable error and retry attempts failed.\n            ValueError: If the parameters are invalid.\n        '
    if ('list_voices' not in self._inner_api_calls):
        self._inner_api_calls['list_voices'] = google.api_core.gapic_v1.method.wrap_method(self.transport.list_voices, default_retry=self._method_configs['ListVoices'].retry, default_timeout=self._method_configs['ListVoices'].timeout, client_info=self._client_info)
    request = cloud_tts_pb2.ListVoicesRequest(language_code=language_code)
    return self._inner_api_calls['list_voices'](request, retry=retry, timeout=timeout, metadata=metadata)
Returns a list of ``Voice`` supported for synthesis.

Example:
    >>> from google.cloud import texttospeech_v1beta1
    >>>
    >>> client = texttospeech_v1beta1.TextToSpeechClient()
    >>>
    >>> response = client.list_voices()

Args:
    language_code (str): Optional (but recommended)
        `BCP-47 <https://www.rfc-editor.org/rfc/bcp/bcp47.txt>`__ language tag.
        If specified, the ListVoices call will only return voices that can be
        used to synthesize this language\_code. E.g. when specifying "en-NZ",
        you will get supported "en-*" voices; when specifying "no", you will get
        supported "no-*" (Norwegian) and "nb-*" (Norwegian Bokmal) voices;
        specifying "zh" will also get supported "cmn-*" voices; specifying
        "zh-hk" will also get supported "yue-\*" voices.
    retry (Optional[google.api_core.retry.Retry]):  A retry object used
        to retry requests. If ``None`` is specified, requests will not
        be retried.
    timeout (Optional[float]): The amount of time, in seconds, to wait
        for the request to complete. Note that if ``retry`` is
        specified, the timeout applies to each individual attempt.
    metadata (Optional[Sequence[Tuple[str, str]]]): Additional metadata
        that is provided to the method.

Returns:
    A :class:`~google.cloud.texttospeech_v1beta1.types.ListVoicesResponse` instance.

Raises:
    google.api_core.exceptions.GoogleAPICallError: If the request
            failed for any reason.
    google.api_core.exceptions.RetryError: If the request failed due
            to a retryable error and retry attempts failed.
    ValueError: If the parameters are invalid.
def list_voices(self, language_code=None, retry=google.api_core.gapic_v1.method.DEFAULT, timeout=google.api_core.gapic_v1.method.DEFAULT, metadata=None):
    '\n        Returns a list of ``Voice`` supported for synthesis.\n\n        Example:\n            >>> from google.cloud import texttospeech_v1beta1\n            >>>\n            >>> client = texttospeech_v1beta1.TextToSpeechClient()\n            >>>\n            >>> response = client.list_voices()\n\n        Args:\n            language_code (str): Optional (but recommended)\n                `BCP-47 <https://www.rfc-editor.org/rfc/bcp/bcp47.txt>`__ language tag.\n                If specified, the ListVoices call will only return voices that can be\n                used to synthesize this language\\_code. E.g. when specifying "en-NZ",\n                you will get supported "en-*" voices; when specifying "no", you will get\n                supported "no-*" (Norwegian) and "nb-*" (Norwegian Bokmal) voices;\n                specifying "zh" will also get supported "cmn-*" voices; specifying\n                "zh-hk" will also get supported "yue-\\*" voices.\n            retry (Optional[google.api_core.retry.Retry]):  A retry object used\n                to retry requests. If ``None`` is specified, requests will not\n                be retried.\n            timeout (Optional[float]): The amount of time, in seconds, to wait\n                for the request to complete. Note that if ``retry`` is\n                specified, the timeout applies to each individual attempt.\n            metadata (Optional[Sequence[Tuple[str, str]]]): Additional metadata\n                that is provided to the method.\n\n        Returns:\n            A :class:`~google.cloud.texttospeech_v1beta1.types.ListVoicesResponse` instance.\n\n        Raises:\n            google.api_core.exceptions.GoogleAPICallError: If the request\n                    failed for any reason.\n            google.api_core.exceptions.RetryError: If the request failed due\n                    to a retryable error and retry attempts failed.\n            ValueError: If the parameters are invalid.\n        '
    if ('list_voices' not in self._inner_api_calls):
        self._inner_api_calls['list_voices'] = google.api_core.gapic_v1.method.wrap_method(self.transport.list_voices, default_retry=self._method_configs['ListVoices'].retry, default_timeout=self._method_configs['ListVoices'].timeout, client_info=self._client_info)
    request = cloud_tts_pb2.ListVoicesRequest(language_code=language_code)
    return self._inner_api_calls['list_voices'](request, retry=retry, timeout=timeout, metadata=metadata)