def __init__(
        self,
        *,
        api_key: str | None = None,
        auth_token: str | None = None,
        base_url: str | httpx.URL | None = None,
        timeout: Union[float, Timeout, None, NotGiven] = NOT_GIVEN,
        max_retries: int = DEFAULT_MAX_RETRIES,
        default_headers: Mapping[str, str] | None = None,
        default_query: Mapping[str, object] | None = None,
        # Configure a custom httpx client.
        # We provide a `DefaultAsyncHttpxClient` class that you can pass to retain the default values we use for `limits`, `timeout` & `follow_redirects`.
        # See the [httpx documentation](https://www.python-httpx.org/api/#asyncclient) for more details.
        http_client: httpx.AsyncClient | None = None,
        # Enable or disable schema validation for data returned by the API.
        # When enabled an error APIResponseValidationError is raised
        # if the API responds with invalid data for the expected schema.
        #
        # This parameter may be removed or changed in the future.
        # If you rely on this feature, please open a GitHub issue
        # outlining your use-case to help us decide if it should be
        # part of our public interface in the future.
        _strict_response_validation: bool = False,
    ) -> None:
        """Construct a new async AsyncAnthropic client instance.

        This automatically infers the following arguments from their corresponding environment variables if they are not provided:
        - `api_key` from `ANTHROPIC_API_KEY`
        - `auth_token` from `ANTHROPIC_AUTH_TOKEN`
        """
        if api_key is None:
            api_key = os.environ.get("ANTHROPIC_API_KEY")
        self.api_key = api_key

        if auth_token is None:
            auth_token = os.environ.get("ANTHROPIC_AUTH_TOKEN")
        self.auth_token = auth_token

        if base_url is None:
            base_url = os.environ.get("ANTHROPIC_BASE_URL")
        if base_url is None:
            base_url = f"https://api.anthropic.com"

        super().__init__(
            version=__version__,
            base_url=base_url,
            max_retries=max_retries,
            timeout=timeout,
            http_client=http_client,
            custom_headers=default_headers,
            custom_query=default_query,
            _strict_response_validation=_strict_response_validation,
        )

        self._default_stream_cls = AsyncStream
Construct a new async AsyncAnthropic client instance.

        This automatically infers the following arguments from their corresponding environment variables if they are not provided:
        - `api_key` from `ANTHROPIC_API_KEY`
        - `auth_token` from `ANTHROPIC_AUTH_TOKEN`
        
src/anthropic/_client.py